Author Topic: EEVblog #315 - Korad KA3005P Review/FAIL  (Read 164783 times)

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Offline EEVblog

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EEVblog #315 - Korad KA3005P Review/FAIL
« on: July 18, 2012, 02:20:08 pm »


Dave.
 

Offline Psi

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #1 on: July 18, 2012, 02:33:48 pm »
I know that beeper sound, it's using a beeper that requires the micro to generate the tone. (They're cheaper than beeper with internal tone generators)

When you try and generate the ~2kHz by setting/clearing the mcu output pin in software other interrupts will semi-randomly delay the set/clear commands and you get a sound that's dirty like that.

To avoid it they need to use the dedicated hardware timer output pin on the mcu so the tone generation happens independently.
(or a beeper that does the tone generation itself)

« Last Edit: July 18, 2012, 02:39:34 pm by Psi »
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Offline snoopen

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #2 on: July 18, 2012, 03:36:12 pm »
Wondering if you'd recommend this over the similarly priced Jaycar lab supply? Looks like they both have an overshoot issue.

This is the one:
http://www.eevblog.com/2009/09/11/eevblog-30-jaycar-bench-lab-power-supply-review/

I recently bought the Jaycar supply, but it's unopened in the box... Thinking I could take it back and get the Korad for the extra $40 or so.
 

Offline snoopen

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #3 on: July 18, 2012, 03:41:44 pm »
Hmmm on second thoughts, I actually finished watching the last 5 mins of the review. Can see why you say FAIL! :O Oh wells!
 

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Offline nitro2k01

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #5 on: July 18, 2012, 03:55:08 pm »
Playing devil's advocate here, but could it be that you've swapped the power input and output on the logic board when reassembling it after the teardown? They seem to be using the same connector.
This way you  might for example have blown the ever so beefy protection diode across the shunt, and later voltage regulation transistor or something else.
« Last Edit: July 18, 2012, 03:57:57 pm by nitro2k01 »
Whoa! How the hell did Dave know that Bob is my uncle? Amazing!
 

Offline dda

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #6 on: July 18, 2012, 04:14:49 pm »
Dave did get into M5 at one point in the vid, but he didnt make any note of it
 

Offline Psi

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #7 on: July 18, 2012, 04:18:07 pm »
Dave did get into M5 at one point in the vid, but he didnt make any note of it

"M5" is Mission Impossible mode for MI5 operatives.

This unit will self destruct in 5 seconds.
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Offline dcel

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #8 on: July 18, 2012, 05:37:11 pm »
Dave

An autopsy would be nice so we can see what failed and showcase your troubleshooting skills for all the young players.

Chris
 

Offline hans

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #9 on: July 18, 2012, 06:28:44 pm »
Honestly, a follow-up would be funny. It would humiliate this PSU even more.

I wasn't impressed with the teardown stage. Everything is 'there' to get a DC programmable PSU, but it seems rubbish built. Uncleaned PCB's, random holes drilled, poor soldering, weird R2R DAC (apparently PCB space and SMT parts placing is free for them) and overall shitty stuff :)

That you have killed it with a 'constant resistance' is too funny. That's like connecting 1 ohm on a 24V output, you should get 5V @ 5A right..

I think the very odd load transients are maybe due to it's unusual current shunt. Seen it in the teardown? It's like more like an inductor of several tenths to hundreds of uH. I would be interested in setting the load transient at turn-off (at least as important as turn-on), will it overshoot due to the inductor?
But unfortunately it's died already :-\

« Last Edit: July 18, 2012, 06:30:42 pm by hans »
 

Offline David Aurora

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #10 on: July 18, 2012, 06:30:36 pm »
My curiosity is killing me here haha, I'm dying to know more about the death of this thing. Did any magic smoke actually escape, or is it software related?
 

Offline Physics_Dude

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #11 on: July 18, 2012, 07:00:22 pm »
Something like this happened to me a while ago with a basic 30v/8A switched mode DC power supply. I think it was a Mastech brand, but I could be wrong. I was using it to power an innocent little project at 6 volts with only a few milliamps, when suddenly at random, the power supply decided to dump a steady 56 volts through the little thing and kill it! :(
Further testing relieved that the power supply was also in a consent current mode of around 8 amps. None of the output adjustment knobs had any effect on the output voltage or current.

It was replaced soon after by a more preferred power supply, but I decided kept the broken one, it seemed quite reliable for supplying the 55-56 volts that it was stuck at.
However, after weeks of abuse on the old one, while I was using it under a fairly heavy load for some extend period of time (the device lacks a cooling fan and will get hot), I heard a few clicks of the relays, and wouldn't you know it, it went back to its normal, advertised operation. I had my full voltage and current limiting controls back too!

I don't use this zombie-like power supply for any serous projects anymore for obvious reasons. It also recently decided to get stuck again in consent current mode at 8 amps. I still have full control over its output voltage though.

I only mention this because Dave seems to have fallen in a similar predicament where his power supply seems to send out its full current capacity at a higher then rated voltage (42.3v at first).
 

Offline Scopeman1

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #12 on: July 18, 2012, 07:11:03 pm »
Just been to TRIO's website.  How well do you know these guys Dave?  Are they any good?  Agilent all over the place.

I saw this on link below......    does not look too bad for the money, and they are local in Sydney.  It's better value than the Jaycar.  It is a triple output for less than the Jaycar dual output cost even with GST & freight!!

http://triosmartcal.com.au/dc-bench-supplies/2432-atten-aps3003s-3d-dual-power-supply-0-30v-3a.html

They have a 150W basic bench supply for $99  http://triosmartcal.com.au/dc-bench-supplies/2631-qje-ps3005-bench-power-supply-150w-0-30v-0-5a.html   It can't be a linear for that price.

As for cheapie scopes, I see they are selling the same scope as Jaycar for almost half the price as Jaycar !!!  WTF!!   They can't be ripping people off at that price or  .... Mr. Jaycar is charging us too much for convenience or ????

http://www.jaycar.com.au/productView.asp?ID=QC1932  jaycar $599 inc GST
http://triosmartcal.com.au/2195-siglent-digital-storage-oscilloscope-25-mhz-bandwith-4-channel.html  = TRIO $298 ex-GST

It's the same scope isn't it? Can you confirm?
 

Offline wiedehopf

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #13 on: July 18, 2012, 07:30:51 pm »
Playing devil's advocate here, but could it be that you've swapped the power input and output on the logic board when reassembling it after the teardown? They seem to be using the same connector.
This way you  might for example have blown the ever so beefy protection diode across the shunt, and later voltage regulation transistor or something else.

I think the power cable leading from the control board to the output ist to short to connect it to the input on the control board. Dave would've noticed the cable being tense, so it's not an error i think he would've made.
But i guess we'll see soon enough when he tracks down the error.
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #14 on: July 18, 2012, 07:35:33 pm »
UPDATE: Triosmartcal have withdrawn it from sale, and Korad are investigating...

Dave.
 

Offline PChi

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #15 on: July 18, 2012, 08:22:04 pm »
Thanks for the video tear down and test.

It might have foldback on the current limit which may be why it was giving inconsistent results with the constant power load.

I am guessing that the output on/off switch just controls the Power Transisters which may have failed Collector Emitter short circuit. The output stage might rely on never having to drive a short circuit when the transformer tap is at the maximum voltage for survival (even with some form of foldback limiting). Possibly Korad need to check the Safe Operating Area of the output transistors. Also cheap power transistors can be unreliable.
 

Offline amyk

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #16 on: July 18, 2012, 08:24:48 pm »
I would've preferred a relay-switched output. Those usually do not fail short (unless the contacts have overloaded and welded together.)
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #17 on: July 18, 2012, 10:30:52 pm »
I would've preferred a relay-switched output. Those usually do not fail short (unless the contacts have overloaded and welded together.)

The golden method of switching voltages in and out without a physical switch but obviously... dickheads-designers
and yes a crowbar is better
« Last Edit: July 19, 2012, 03:13:22 pm by DaveXRT »
 

Offline Greg J

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #18 on: July 18, 2012, 11:18:59 pm »
Chinese quality. I don't think anyone was hoping this will work for this price.
Even their website is one big fail.
« Last Edit: July 18, 2012, 11:21:02 pm by Greg J »
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don't turn it on, take it apart !
 

Offline Stephen Hill

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #19 on: July 18, 2012, 11:28:00 pm »
Even their website is one big fail.

What's wrong with their website?
http://koradtechnology.com/en/
 

Offline Bloch

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #20 on: July 19, 2012, 12:26:01 am »
 

Offline Rufus

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #21 on: July 19, 2012, 12:26:14 am »
It is pretty obvious the main series regulating transistor failed short circuit providing an unregulated supply from whatever the transformer tap relays have selected.

When you start putting effective shorts on the output with the supply set to high voltage the pass transistor experiences maximum stress until the relays tap down the transformer. Probably an SOA failure because the output transistor is grotty or marginally specified.

On 'funny things going on' understand a constant power load with no volts applied is trying to be a short circuit so when you switch a supply on to it the supply ought to go straight into current limit and stay there delivering insufficient power.

The load probably has a minimum turn on voltage setting/option where it won't start drawing current till the voltage reaches that value as a workaround for the problem.

When you turn on a constant power load with a supply already connected it is a race between the load reducing the current draw and the supply going into current limit.
 

Offline slburris

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #22 on: July 19, 2012, 12:49:19 am »
I almost wonder if they are doing something stupid, like implementing the control
loop in the processor, given the strange ramps at turn on.

Of course you would get terrible transient response doing it that way, but
I've seen designs on the net doing just that.

Scott
 

Offline firewalker

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #23 on: July 19, 2012, 01:15:52 am »
The machines that checks if a chip passes all the tests what does with the rejected ones? Maybe makes a mark on the surface? Just saying... You know, sanded chips...  :P :P :P

Alexander.
Become a realist, stay a dreamer.

 

Offline Electr0nicus

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #24 on: July 19, 2012, 01:56:45 am »
Most high current linear power supplies use more than one series transistor. They are usually paralleled and to eliminate thermal runaway there are current balancing resistors used. Maybe there are no, or insufficient current balance resistors used in this PSU, so one transistor gets most of the current and self destructs, so the other transistor also gets the maximum current and gets destroyed too.
« Last Edit: July 19, 2012, 01:59:14 am by Electr0nicus »
 

Offline pickle9000

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #25 on: July 19, 2012, 02:26:07 am »
I think the biggest problem here is the level of "cheaping out". 3 or 4 shortfalls and the product hits the floor. The manufacturer could turn this into a win by fixing the problem and then sending out a few copies to be reviewed. I would certainly buy a product that has been redone and brought up to snuff.

The fact that they cut corners, case, finish, design, lack of cleaning and so on are an issue but if it fails out of the box your name is mud. The unit has a good front panel layout, simple to operate form factor, so a win there.

Looking at the web site you can see that most of their product line is based around a variant of this unit. That being the case I hope they have the incentive to fix it.

Is this another example of Chinese manufacturing cheaping out. Yes, and extra 10 bucks per unit and this may have been an acceptable product. I'm not saying great but OK for the money.

Can you blame the engineer, the build team, management. Yes all of the above.

...mike
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #26 on: July 19, 2012, 02:28:59 am »
I usually side with HK companies
but it all changed with this event  8) nah i'm kidding, just not this one. For now.
 

Offline gxti

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #27 on: July 19, 2012, 03:18:40 am »
I agree that some of the early weirdness during testing is probably due to the control loops of the load and the supply interacting in non-obvious ways. But then the thing burnt itself out, no excuses there!
 

Offline LaurenceW

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #28 on: July 19, 2012, 05:11:33 am »
Well, by the time I got here, others had already made the same points! But I concur:

  • It looks like the design uses a software loop for voltage stabilisation, hence the ramps (up and over) while the software catches up. NEARLY ALWAYS BAD.
    I wonder if your earliest glitches when the output died were software related?
    The soft on/off switch will probably work by simply turning off the base drive to the (two) main series pass transistors. Since current continues to flow, that suggests fried output devices (or possibly fried common driver).
    The internal voltmeter probably maxes out at around 36V (was it?) because in normal use it would never even need to go that high. Under fault conditions, the output rises above this to the main supply cap figure, however. And at 57V, that seems a bit OTT anyway for a 3OV power supply.
    I doubt that encoder is "optical" - just a simple two-switch affair. CHEAP!
    I didn't like the quality of the PCB design, at all. Not laid out by a seasoned designer. Inconsistent use of vias, track widths and routing styles.
    The discrete D>A converter seems bonkers. Surely there are plenty of fine chip solutions which would use less components, hence less PCB real estate, assembly time, etc.?
SMUG MODE :[ON] I've just bought me a new  end-of-line TTI 3 channel power supply PL330TP  (30v x 3A). It is built like a brick dunny (as I think the antipodeans would say). The only problem with it is the HERNIA it gives me when I try and pick it up. It will still be going strong when I am long dead. Pays yer money. I might do a teardown one day.
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Offline hans

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #29 on: July 19, 2012, 05:46:20 am »
All power supplies fail.. At college we had an Agilent 3630A triple output. We used it to power a transistor signal amp of +/-10V.
There was an unit that was faulty on -10V, where it would ramp up to -30V and sometimes stay there (the panel meters indicated , but the scope confirmed). So, yeah, that kinda sucks if you make fireworks TWICE with tantal caps of 16V as decoupling. Oh well. At least we made fun of each other when caps blew up on the negative rail (ah you screwed that up mate!) and then it happens to myself the day after.  :-X Then we figured out the PSU was bad..  ::)

The overall quality of this supply is really crap. When I saw I thought, yeah, it will do 30V/5A for a few moments and then explode in flames. Not built to last. The PCB's are dirty, soldering is bad, bodges everywhere, weird case construction, weird DAC, the current shunt looks more like an inductor (dave, can you measure it? :D - maybe it explains a part of the weird load transients, unfortunately it's now fried but the turn-off response would be interesting too), weird holes/isolation idea.

Furthermore, an R2R dac is a horrible concept. If you read the WIKI, you need to have matched resistors for that. Well, you can take them from the same batch, but as Dave showed with his batch measurements some time ago: 1% resistors measured over a range of 1000s will have a variation of 0.5% - 1%. I see they stacked up 16-bits for current and voltage. That's just a bullshit thing. I bet the actual accuracy isn't that great. Furthermore, if you control  3000 to 5000 counts, why do you need it?
Apparently PCB space and assembly is free there!

Furthermore, the relay switching seems too slow. Too little capacitance? 6800uF at 5A & 100Hz isn't a great deal.
I can understand them switching the relays.. They of course look at the live output voltage (after current limiting) and make sure the voltage difference across the transistor isn't too large. Those other cheap PSU's recently linked here do the same, and basically have the same problem. I've encountered this a few times on a rather large buck-boost LED driver.

I basically tried the same abuse. Put the output at 30V/5A, and turn on a 60W load with 15A inrush currents. The output drops to 3V/5A, and that's it. The PSU didn't die, though.
« Last Edit: July 19, 2012, 05:54:46 am by hans »
 

Offline ivan747

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Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #31 on: July 19, 2012, 06:54:52 am »
UPDATE: Triosmartcal have withdrawn it from sale,

The thing I am asking myself is what was the procedure Triosmartcal used to decide to add it to their offerings?

Did they get a sample from Korad? Did they at least open it? Was the sample a special or from the normal production? Did they at least checked one when they took delivery of the batch they ordered? Did they check the manual for completeness?

Quote
and Korad are investigating...

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Offline ivan747

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Nothing like the smell of rosin core solder in the morning.
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Offline ivan747

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #33 on: July 19, 2012, 07:12:16 am »
I almost wonder if they are doing something stupid, like implementing the control
loop in the processor, given the strange ramps at turn on.

Of course you would get terrible transient response doing it that way, but
I've seen designs on the net doing just that.

Scott

+1
Nothing like the smell of rosin core solder in the morning.
"Could you not use some of that crowdfunded $1.5 million to hire a graphic designer who understands perspective?" -Delta
"A soldering station I bought once had a sticker on it that said, I shit you not, 'QENUINE'." -c4757p
 

Offline Electr0nicus

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #34 on: July 19, 2012, 07:58:47 am »
The white residue comes from cleaning the PCB with an acetone like solvent. Acetone breaks up the molecular bonds of the flux leaving back this white substance if not washed off thoroughly . This indicates that they actually don't wash the PCBs in the solvent, but rather only dipping it into. When the solvent dries off, the flux is still there, with the difference, that it is now a white powdery substance, due to the broken up molecular bonds. You can easily brush it off using an old toothbrush f.e.  I know that, because I myself use acetone the most time to clean my homemade PCBs. Of course, you have to know, what plastics are on the board, because f.e. PVC gets attacked by the acetone. But apart from that, almost all plastic components on a PCB are acetone tolerant.
« Last Edit: July 19, 2012, 08:01:53 am by Electr0nicus »
 

Offline wiedehopf

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #35 on: July 19, 2012, 08:06:04 am »
Regarding:
Thread Original Video at 18:30

Once the Power Supply is in CC Mode, the constant power load will further reduce it's resistance and hence the Voltage across the load drops to near nothing.
How it gets there is beyond me.
Perhaps the initially low load resistance sucks dry the power supplies capacitors and when recharching them the supply goes into CC mode. Just a guess.
But that is not sth bad i'd say. Where in real life do you have a constant power load?

The breakdown on the other hand is really bad news. And escpecially the Over Volt Protection really works like a CHARM :)

Edit: grrrr ... auto youtube embedding destroyed the timecode so i took it out
« Last Edit: July 19, 2012, 06:22:26 pm by wiedehopf »
 

Offline Electr0nicus

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #36 on: July 19, 2012, 08:24:38 am »

The breakdown on the other hand is really bad news. And especially the Over Volt Protection really works like a CHARM :)

There are power supplies out there, which generate a overvoltage condition, that is not so obvious like on the Korad PSU. I f.e. have a ELV PS9530 30V 10A PSU and one day I discovered mostly by accident, that it puts out a huge overvoltage pulse when switched off (proper mains power switch).
http://www.mikrocontroller.net/attachment/70639/PS9530_KM_G_071030.pdf
This phenomenon only occurred when the relay was switched on and thus the two transformer taps were connected in series to deliver a output voltage >15V. I found out, that it was actually a design glitch with the freewheeling diode of the relay, thus the control circuitry was influenced and switched on the serial pass transistors completely, delivering 40V to the output for at least 20ms. I found a solution to prevent that and emailed it to the company, which has designed the PSU. But they weren't even interrested in solving the problem and said that "because nobody had ever complained yet/found it out, they wouldn't bother correcting the mistake they made". Absolute dickheads.
But end of rant! What I want to say, is that even if you buy a higher priced PSU, (mine costed 359€/425AUD) you are not immune to such problems. 
« Last Edit: July 19, 2012, 08:29:17 am by Electr0nicus »
 

Offline free_electron

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #37 on: July 19, 2012, 08:51:55 am »
The white residue comes from cleaning the PCB with an acetone like solvent.
cleaning pcb's in acetone is not done. acetone eats too many plastics. the displays for example would melt ... same for at exle of the rotary encoder ..

this residue is most likely water soluble flux that has not fully saponofied and washed away.
water soluble flux is hygroscopic and will yield the classic white soap-scum appearance if not washed properly.

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Any comments, or points of view expressed, are my own and not endorsed , induced or compensated by my employer(s).
 

Offline Electr0nicus

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #38 on: July 19, 2012, 09:07:07 am »
The white residue comes from cleaning the PCB with an acetone like solvent.
cleaning pcb's in acetone is not done. acetone eats too many plastics. the displays for example would melt ... same for at exle of the rotary encoder ..

this residue is most likely water soluble flux that has not fully saponofied and washed away.
water soluble flux is hygroscopic and will yield the classic white soap-scum appearance if not washed properly.

Thanks free_electron!
I didn't know that up to now.
As I wrote, I use acetone to clean my PCBs, when there are no sensitive plastics on the board. Then I get the same type of white residue, but it's not soapy but powdery.
If this residue is hygroscopic, then I assume it must be a acidic or basic? Or I'm completly wrong. So if it's a base or acid, then this will be conductive soapy layer on the whole board, which can't be good  ???
« Last Edit: July 19, 2012, 09:09:06 am by Electr0nicus »
 

Offline Denno

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #39 on: July 19, 2012, 09:12:50 am »
Almost certainly a blown pass transistor in the series regulator. Be interesting to see the part number on the MOSFETs to see if they are under rated. The is why some form of crowbar output protection is employed in better engineered supplies. If the output goes higher than some threshold then an SCR or transistor shorts it to ground and blows the supply fuse. Supply still needs to be fixed but does not take your circuit with it.

The test with the constant load of 50W where output was dropping to 0.2 volts was understandable at the electronic load would present an almost dead short when the supply output was switched on. A better test is to use the load switch on the dummy load to turn the constant power load on and off. This way the electronic load sees the set supply voltage and only switches in the appropriate current load for the power setting.
 

Offline Bloch

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #40 on: July 19, 2012, 09:22:08 am »
The is why some form of crowbar output protection is employed in better engineered supplies. If the output goes higher than some threshold then an SCR or transistor shorts it to ground and blows the supply fuse. Supply still needs to be fixed but does not take your circuit with it.


Why not a relay ? Is it not fast enough ?
 

Offline JoannaK

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #41 on: July 19, 2012, 09:38:53 am »
UPDATE: Triosmartcal have withdrawn it from sale, and Korad are investigating...

Dave.

Next time.. Try to get some smoke out of it  ;D
 

Offline free_electron

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #42 on: July 19, 2012, 11:01:51 am »
The is why some form of crowbar output protection is employed in better engineered supplies. If the output goes higher than some threshold then an SCR or transistor shorts it to ground and blows the supply fuse. Supply still needs to be fixed but does not take your circuit with it.


Why not a relay ? Is it not fast enough ?
A relay is slower than an SCR to kick in but the main reason lies elsewhere
a relay needs power to energize and close itself... shorting the power rail .... removes the power from the relay ... so that relay would become  buzzer .... until the fuse pops
under a certain voltage the relay will also not have enough megnetic pull to close the switch...

an SCR is triggered on its gate and stay s in conduction until the current through it has fallen under the hold current. this hold current can be very low.
So: fire the SCR and it stays in conduction until the fuse is blown and the capacitors in the circuit are discharged far enough that the current has dropped to a few milliampere. Then it comes out of conduction . the voltage across the scr can be 0.1 volt . it doesn't care as long as there is current flowing it stays on.
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #43 on: July 19, 2012, 11:26:37 am »
Greetings and thanks for all the feedback.

Firstly yes we have withdrawn this from sale until we get to the bottom of the failure. To answer the previous question about what process do we use to decide what to sell, well we have a process and this passed it.

We got two samples a 30V 5A and a 60V 2A.  As an ISO-9001:2008 accredited company, a structured product introduction process is mandatory. We look much further than just the build quality. We look at support scenarios and how we and the supplier can deal with them so :
- what is the warranty?
- Can we repair locally?
- Is there a calibration procedure?

The  samples do get pulled apart. For example the white residue on the boards was known to us, we've seen it on more than one suppliers' boards and it has never been a reliability issue.

For the price as Dave says the build quality was aceptable and we liked the user interface too.
We also have already fed back the incompletness of the manual plus we'd like to see the programming commands in there too.

Our performance testing entails putting a product through our NATA accredited calibration lab to make sure it meets its specifications which these supplies did. (NATA is similar to UKAS , NVLAP etc) Thanks to Dave's dynamic (in more than one sense of the word)  testing of the supply a potential weakness has been exposed that the placid conditions of a Cal lab would not reveal. The product was immediately pulled from sale as we will not sell a product we don't have 100% confidence in, and after Dave's review we have our doubts on this one until we get a manufacturer recommendation and/or rectification proces.  We are certainly not scared of putting a product through an EEV Blog tear down and product review as the result can only be beneficial for customers, us and of course the manufacturer that will need to act on the findings so that the market gets better products and we get happier customers.

We try to offer two classes of product and if you visit our web site   www.triosmartcal.com.au  you will see this in action. We offer world class brands like Agilent, but sometimes that's not what people need or can afford. Wants and needs are different. So for folks with budget constraints, or simply needing something that does not have a world class brand label on it we try to offer lower cost, value-for-money reliable products that do what they are supposed to do. Plus we need to be able to support  our customers locally after they have bought something from us. Our customers are everything to us, it does not matter how good our products are without happy customers and good staff to look after them we won't be here.

There is a formula used in marketing-speak that is very simple but very true:

Value = (Performance/Price) + Service .........OK I know the brackets are redundant but most marketers are not engineers.  Many people do not consider service when buying a product but it is an integral part of acquiring and owning a product.

The other true marketing statement is that "you get what you pay" for. Well it's mostly true unless you are being ripped off. So our challenge is to choose products that meet these criteria. We thought this power supply met our criteria and until we are sure it does, it is withdrawn from sale. By the way we know it is cheaper in the USA. That is to do with volumes when purchasing, freight costs, customs clearance etc. We set our prices to be competitive, offer value for money and provide an adequate return for the company so we are still here for you if something does go wrong. It is all a big balancing act. Proof of this can be seen in another post I saw on here comparing our price on a 25MHz digital scope to a much larger company's price here in Australia. We are almost 50% less expensive and at that price we meet all our criteria necessary to take that scope to market. (thanks to whoever did that for pointing that out).

Ultimately you pay your money and make your choice. At $199.00 +gst here in Australia it is competitively priced for a locally sold and locally supported product.  If we find out afterwards that something does not perform as initially expected, we won't sell it.  We have sold a few of these and have not had any returns. Nevertheless we did not know it could not handle the Dave treatment and now that we do know, it is off-sale.  For folks that want a main brand, the big-guns are coming down in price.  You can pay $360+gst and get an Agilent U8001A with 30V 3A. It is an excellent product for the price. Maybe Dave should do a tear down on one of those for comparison.

Anyway I hope that answers your question and also why we have withdrawn this product from sale. Until we know the reason for the FAIL and the preventative fix it stays off-sale. Dave has full permission to rip it to bits to find out what went wrong as it seems there is quite a bit of interest in this.  Just don't drive over it please Dave ;-)

« Last Edit: July 19, 2012, 12:14:56 pm by TRIO_Smartcal »
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Offline grenert

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #44 on: July 19, 2012, 12:58:56 pm »
Unless you really need the programmability or the digital display, I think many people would do much better (at the same price) with an old tank of a power supply like this one:
http://www.ebay.com/itm/HP-6227B-Dual-DC-Power-Supply-W-Option-40-0-25V-0-2A-30-Day-WARRANTY-/300743973561?pt=LH_DefaultDomain_0&hash=item4605bcdab9

There will certainly be no funny business with it!
 

Offline amspire

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #45 on: July 19, 2012, 01:18:20 pm »
Unless you really need the programmability or the digital display, I think many people would do much better (at the same price) with an old tank of a power supply like this one:
http://www.ebay.com/itm/HP-6227B-Dual-DC-Power-Supply-W-Option-40-0-25V-0-2A-30-Day-WARRANTY-/300743973561?pt=LH_DefaultDomain_0&hash=item4605bcdab9

There will certainly be no funny business with it!
Hey, that is my power supply!

It is a good supply, reasonably compact (compared with other supplies of the same vintage) and no fan to annoy you or to fail.  Proper independent thyristor based overvoltage circuit for when you are testing that board you cannot afford to accidentally damage.

For average use, I prefer the moving coil meters to the digital readout. I like having a coarse voltage and current control that can go from 0V to maximum in a single twist.

Richard.
 

Offline ivan747

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #46 on: July 19, 2012, 01:51:48 pm »
The is why some form of crowbar output protection is employed in better engineered supplies. If the output goes higher than some threshold then an SCR or transistor shorts it to ground and blows the supply fuse. Supply still needs to be fixed but does not take your circuit with it.


Why not a relay ? Is it not fast enough ?

It's too slow. About 3 orders of magnitude slower than a good transistor. Relays take milliseconds to switch. You don't want your $2000 dollar 1.8V prototype being exposed to 30V, do you? It is not uncommon to see transistors switching in tens of microseconds. Although, I reckon the slowest component in a overvoltage protection circuit would be the fuse.
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Offline Alexei.Polkhanov

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #47 on: July 19, 2012, 02:06:36 pm »
I have BK PRECISION 9110 on my table right now. I got it for $299 from Newark. I connected it to 10 ohm resistor, set current limit to 20mA, voltage - 10V and pressed ON button - result is what seems to me rather large overshoot in voltage (see attached photo). This is is the only lab supply I have right now. It is a new device, good brand,  so I am not sure if it is so unusual to see large overshoot on these supplies in current limiting mode, unless you want to spend over $2000.
After all what matters, in my opinion, is power delivered to connected device over set limit in watts not how high voltage is or in other words 10v overshoot for 100ns is better than 500mV overshoot for 100ms, right?
 

Offline Scopeman1

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #48 on: July 19, 2012, 02:36:43 pm »
That looks worse than the KORAD.  Also BK Precision re-badge other products, like the Siglent Scopes, the Atten spec-an, Protek HH-spec-an and some of the power supplies look similar to those on Extech's website.  It would be great of someone started a cross-reference for all this re-branding nonsense so we can buy from the OEM and cut-out the big-name companies adding the brand name and price tag.  As for Alexei's power supply, does it say "made in China on the back panel?"
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #49 on: July 19, 2012, 02:58:12 pm »
Greetings and thanks for all the feedback.

Firstly yes we have withdrawn this from sale until we get to the bottom of the failure. To answer the previous question about what process do we use to decide what to sell, well we have a process and this passed it.

*snip*

Thanks for the detailed reply Charles.
I will try and find some time to investigate what failed on it...
Would of course be nice if Korad released the schematic!  ;)

Dave.
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #50 on: July 19, 2012, 03:17:33 pm »
That looks worse than the KORAD.  Also BK Precision re-badge other products, like the Siglent Scopes, the Atten spec-an, Protek HH-spec-an and some of the power supplies look similar to those on Extech's website.  It would be great of someone started a cross-reference for all this re-branding nonsense so we can buy from the OEM and cut-out the big-name companies adding the brand name and price tag.  As for Alexei's power supply, does it say "made in China on the back panel?"

Most of the extech's are manson PSUs too


But the best way to OVP is a independent SCR adjustable monitoring circuit
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #51 on: July 19, 2012, 03:38:02 pm »
Greetings and thanks for all the feedback.

Firstly yes we have withdrawn this from sale until we get to the bottom of the failure. To answer the previous question about what process do we use to decide what to sell, well we have a process and this passed it.

In other words, you sailed hard on the wind, but this time the wind got the upper hand. Time to change your process to apply a more conservative pass criteria?

Quote
We got two samples a 30V 5A and a 60V 2A.  As an ISO-9001:2008 accredited company,

Can we skip that ISO thing, please? After decades in the industry, taking part in multiple accreditations, and having had to game the system daily for long periods of time I have nothing good to say about it.


Quote
The  samples do get pulled apart. For example the white residue on the boards was known to us, we've seen it on more than one suppliers' boards and it has never been a reliability issue.

The thing with the flux residue is you can't know its long term effects, e.g. if that particular residue is corosive over time. You just don't know the manufacturing process and what they used.

And lets just say, as a calibration company you should have got very, VERY nervous about that DAC. That is your core bussines.
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Offline free_electron

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #52 on: July 19, 2012, 04:07:47 pm »
Can we skip that ISO thing, please?
ISO : The process can be total crap , as long as it is described in detail and meticulously followed.. ISO only verifies you:

1) have a process
2) follow it
3) can track it

as for the process itself : that may be 'put on tin foil hat , chant rama rama hare hare, put left big toe in right ear and sign form 123-a at the dotted line.'
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Offline Scopeman1

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #53 on: July 19, 2012, 04:28:50 pm »
I disagree with Mr. Bored  not having much good to say about ISO,  many others do have good things to say and look for ISO accredited vendors. It forces a process and a standard on to a company. Agreed that compliance is a pain in the a$$  but it sets a level people can judge a company by.   If  Mr.Bored@Work fudged it or worked around it  then he's only fooling himself and anyone who did business with his company.  As for putting on a tin foil hat and chanting rama-rama-guru as part of a power supply test, I suspect most ISO accredited companies probably choose more relevant criteria as part of their processes.

We buy based on the performance spec. and the price, plus previous experience with a vendor.  Charles' formula about value, performance and service makes sense. If they test to the performance spec it is sold under and it meets that spec and they can support it if it goes wrong then that seems reasonable and I'd buy from them.  The fact that they stopped selling the item immediately is also good.  It shows they put quality, and not putting potentially flawed products into the market before making profit. Even big names like Fluke etc  issue recall notices and withdraw products from sale if there is an problem with them so what Trio has done is the right thing to do.

Mind you I agree on the testing process, perhaps more a few more real world operational tests in addition to a cal-lab performance verification might uncover this sort of thing before Dave gets his hands on it. I think they sell electronic loads too so maybe they should test both together ;-).  Probably though a batch test would be the way to go when something like this is uncovered to see if Dave got the lemon or a normal product.

No opinion on the DAC really, if it does its job as Dave says what the heck!!!  I hope Dave does a tear-down to find the problem with it.  Anyone want to start a poll to guess the fault?
 

Offline dda

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #54 on: July 19, 2012, 04:39:28 pm »
I think people are being a bit hard on our scope-crushing friend. He isn't in the business of selling something faulty on purpose. If Dave hadn't busted it before he finished the review he probably would have given it a conditional thumbs up. And it wasnt completely faulty at the beginning.

Chillax bros.
 

Offline Bloch

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #55 on: July 19, 2012, 04:53:16 pm »
Would of course be nice if Korad released the schematic!  ;)


I have heard rumors that they are in process with striking out all component values with a thick black marker  ;D
 

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #56 on: July 19, 2012, 05:15:37 pm »
Time to change your process to apply a more conservative pass criteria?
For a sub $200 supply? Guess you haven't been taking you reality pills for sometime, eh Bored? Trio Smartcal have taken all appropriate action. Did you expect weeks of destruction testing?

Quote
Can we skip that ISO thing, please? After decades in the industry, taking part in multiple accreditations, and having had to game the system daily for long periods of time I have nothing good to say about it.
Why? It's the tool of delight for desk cowboys like yourself. A long winded way of saying all care, no responsibility.

Quote
Quote
The  samples do get pulled apart. For example the white residue on the boards was known to us, we've seen it on more than one suppliers' boards and it has never been a reliability issue.

The thing with the flux residue is you can't know its long term effects, e.g. if that particular residue is corosive<sic> over time. You just don't know the manufacturing process and what they used.
If it's corrosive? If it radioactive it could sizzle your gonads too, however if is very much the operative in either wild guess. Seems you've avoided reading the highlighted portions of the suppliers comments, it certainly appears they have a lot of prior experience applied in their judgements .

Quote
And lets just say, as a calibration company you should have got very, VERY nervous about that DAC. That is your core bussines.<sic>
Who the hell seriously calibrates (or has calibrated) a sub $200 instrument? that's hairy palm stuff! An occasional quick tweak would satisfy anyone sane.
« Last Edit: July 19, 2012, 05:42:31 pm by Uncle Vernon »
 

Offline amspire

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #57 on: July 19, 2012, 05:35:24 pm »
Can we skip that ISO thing, please? After decades in the industry, taking part in multiple accreditations, and having had to game the system daily for long periods of time I have nothing good to say about it.
Why? It the tool of delight for desk cowboys like yourself. A long winded way of saying all care, no responsibility.


The thing I love about ISO-9001 is you can make the lowest quality and least reliable piece of gear in the industry, but as long as the documentation correctly describes this low quality unreliable design and construction, you are a fully complying with the 9001 quality standard.

You can make the best and most reliable piece of gear in the world, but if you do not follow the correct paperwork procedures (i.e. the procedures you committed to when you set up ISO9001 for the firm)  when you identify and correct problems, you are failing 9001.

If your ISO9001 implementation specifies a procedure where all reports of problems are entered on the correct form with the correct number and then shredded, that would probably be fine for ISO9001 as long as you actually shred all the forms, and record the shredding in another document. In this case, if someone instead reads the forms and corrects the problems, that would be an ISO9001 quality control failure for the firm.

Richard.
« Last Edit: July 19, 2012, 05:39:25 pm by amspire »
 

Online ejeffrey

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #58 on: July 19, 2012, 05:54:15 pm »
I disagree with Mr. Bored  not having much good to say about ISO,  many others do have good things to say and look for ISO accredited vendors. It forces a process and a standard on to a company. Agreed that compliance is a pain in the a$$  but it sets a level people can judge a company by.

No, it doesn't. Without knowing the documented practices, ISO certification only tells you that a company likes paperwork.  I don't think it is bad or worthless per se, but it should be an internal matter.  If ISO9000 certification helps you organize the internal operation of your company and improve quality control, go for it, but it isn't really anything your customers should have any reason to care about.  It is like if you told your customers that "We only use full spectrum fluorescent bulbs in all our offices to maximize worker productivity"  ISO9000 is certainly no substitute for good quality control practices.

That said, I don't expect much from a distributor of a $100 programmable power supply.   That falls squarely in the "you pays your money and you takes your chances" category, and anyone who pays that little for a power supply should know it.
 

Offline Alexei.Polkhanov

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #59 on: July 19, 2012, 06:07:33 pm »
As for Alexei's power supply, does it say "made in China on the back panel?"

Nope, dos not have any indication where it was made - probably there was something on a box which I have disposed. I have opened it and inside it is all different from KORAD although front panel has some strong resemblance.

Looking at Datasheet for Agilent E36XXA series which I may need to buy because I need dual supply with tracking
Transient Response Time: "< 50 ?sec following a change in output current from full load to half load for output to recover within:" 10 mV 15 mV (15mV for more powerful versions).

That is MICROseconds. My supply does not even have Transient Response Time in datasheet.
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #60 on: July 19, 2012, 06:27:10 pm »
Mind you I agree on the testing process, perhaps more a few more real world operational tests in addition to a cal-lab performance verification might uncover this sort of thing before Dave gets his hands on it. I think they sell electronic loads too so maybe they should test both together ;-).  Probably though a batch test would be the way to go when something like this is uncovered to see if Dave got the lemon or a normal product.

I also could have lucked upon a particular load condition which causes the unit to fail, that may very well be next to impossible to find with normal acceptance testing. We just don't know unless more units are tested.

Quote
No opinion on the DAC really, if it does its job as Dave says what the heck!!!  I hope Dave does a tear-down to find the problem with it.  Anyone want to start a poll to guess the fault?

Most likely a shorted pass transistor of some description.
My guess would be it was being pushed outside of it's SOA (Safe Operating Area).
The likely underspeced heatsink (without doing some calcs & measurement) won't help in respect.

Given that Korad don't publish the performance curves of the scopes, the customer does not know the power limits over the voltage range. Without that info, you have to assume it can handle worst case 150W (30Vx5A) load at any output voltage and transformer tap. In practice, with linear supplies, it ain't that simple, unless they are overengineered like a brick dunny.

Dave.
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #61 on: July 19, 2012, 07:01:24 pm »
Official response from Korad (in part):

Quote
What you received was the early delivery and in this delivery, there is something wrong with those transistors. And we have improved since that shipment.

Quote
As for 60V, 2A, the transistor on it is good. Don't worry. And this won't happen again.

So there you go, under specced (or dodgy) transistors, surprise, surprise!  ::)
Genuine high power transistors are not cheap, and have been scammed on the grey market for several decades now. Wouldn't surprise me if Korad got duped.

Dave.
« Last Edit: July 19, 2012, 07:03:01 pm by EEVblog »
 

Offline TradieTrev

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #62 on: July 19, 2012, 07:06:58 pm »
Great to see Korad live up to the expectation one would expect using on a psu!  ;)
 

Online janoc

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #63 on: July 19, 2012, 07:14:46 pm »
Official response from Korad (in part):

Quote
What you received was the early delivery and in this delivery, there is something wrong with those transistors. And we have improved since that shipment.

Quote
As for 60V, 2A, the transistor on it is good. Don't worry. And this won't happen again.

So there you go, under specced (or dodgy) transistors, surprise, surprise!  ::)
Genuine high power transistors are not cheap, and have been scammed on the grey market for several decades now. Wouldn't surprise me if Korad got duped.

Dave.

Hmm dodgy vendor selling gear with dodgy parts from who knows where. With something like a PSU that can deliver so much power, that is literally asking for lawsuit when it blows up in someone's face ...
 

Offline hans

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #64 on: July 19, 2012, 07:44:54 pm »
Official response from Korad (in part):

Quote
What you received was the early delivery and in this delivery, there is something wrong with those transistors. And we have improved since that shipment.

Quote
As for 60V, 2A, the transistor on it is good. Don't worry. And this won't happen again.

So there you go, under specced (or dodgy) transistors, surprise, surprise!  ::)
Genuine high power transistors are not cheap, and have been scammed on the grey market for several decades now. Wouldn't surprise me if Korad got duped.

Dave.

In that case they can sent a new production model (or maybe Trio Smart Cal has some) and give it some more Dave treatment? :D

Well, yeah, pre production models can fail. You had the Agilent scope also failing with the extension card board. They fixed the issue and now it works fine. So I guess it happens all over the industry.
 

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #65 on: July 19, 2012, 08:37:54 pm »
Hmm dodgy vendor selling gear with dodgy parts from who knows where. With something like a PSU that can deliver so much power, that is literally asking for lawsuit when it blows up in someone's face ...

We do not know if they are dodgy parts, that's just speculation. They may very well be genuine parts, but accidentally installed the wrong type or something.

Dave.
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #66 on: July 19, 2012, 08:40:53 pm »
Well, yeah, pre production models can fail. You had the Agilent scope also failing with the extension card board. They fixed the issue and now it works fine. So I guess it happens all over the industry.

Just on my blog alone there is the Agilent 3000 scope, the Extech 505 meter, the Extech pen meter, the BK Precision LCR meter, and the Agilent U1272A meter (any others?)

So yeah, it happens all the time. Most are never made public.

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Offline mikeselectricstuff

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #67 on: July 19, 2012, 08:59:32 pm »
Well, yeah, pre production models can fail. You had the Agilent scope also failing with the extension card board. They fixed the issue and now it works fine. So I guess it happens all over the industry.

Just on my blog alone there is the Agilent 3000 scope, the Extech 505 meter, the Extech pen meter, the BK Precision LCR meter, and the Agilent U1272A meter (any others?)

So yeah, it happens all the time. Most are never made public.

Dave.
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #68 on: July 19, 2012, 09:26:23 pm »
When we get a fix for this and an up to date production unit, Dave will get another to do his best to let the smoke out. When he does and IF it gets a thumbs up, we'll give it an extra years warranty at our cost. Until then it stays off sale.

As for the ISO thing, I totally agree on the fact you can document any procedure, show compliance, prove it to an auditor etc..... But it simply comes down to the question " is the procedure relevant and beneficial to your business and will your customers benefit because you have these processes?" We believe it does.

While  a process that involves wrapping one's head in tin foil, while singing Hare Krishna with a toe in one's ear, be it your toe or that of an intimate friend,  might  be a process that is repeatable, documentable, auditable, and for some trolls perhaps an enjoyable process, strangely enough it's not one we use in the selection and supply of test equipment. Others might, we don't    ;D
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Offline Rufus

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #69 on: July 19, 2012, 09:40:32 pm »
I disagree with Mr. Bored  not having much good to say about ISO,  many others do have good things to say and look for ISO accredited vendors. It forces a process and a standard on to a company. Agreed that compliance is a pain in the a$$  but it sets a level people can judge a company by.

Just lol - the only people with good to say about ISO 9001 are those making a living from it.

ISO 9001 is widespread because like a virus and by design it is contagious, not because it does anything useful.

But it simply comes down to the question " is the procedure relevant and beneficial to your business and will your customers benefit because you have these processes?" We believe it does.

And when the answer is yes but could be improved (as Dave appears to have demonstrated) ISO 9001 is going to make changing them more difficult and expensive.
 

Offline poorchava

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #70 on: July 19, 2012, 09:48:18 pm »
Hmm, I wonder if Korad is really going to remove the issue and use higher spec/ quality brand transistors will there be any way to tell bad and good versions apart? I wanted to buy that from Korad distributor here in Poland (they mainly deal in rework equipment like IR stations, BGA reballing stuff, soldering irons, chemistry etc) but now i guess I want to know how to tell if they are selling 'good' or 'bad' version (of course assuming that Korad will really do what they say and that this was early/preproduction batch that Triosmartcal received)

ISO is total bull****. I'm facing that daily... (dealing quite alot with quality management iny my company) Even companies that are considered "quality" "brand name", having all the certificates ISO, TUV, OMG, WTF and probably even pope's blessing in written form often make such bad screwups that you would never think it's possible. And the field actually doesn't matter... semiconductor, passives, inductives, mechanical parts, chemistry, metal cast parts, nearly everything.
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Offline hans

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #71 on: July 19, 2012, 10:30:06 pm »
Going further offtopic about ISO...

At my graduation place we had ISO9001 stuff too. All footprints, symbols , datasheets, etc. should be 'released' (thus verified) and organized on the servers. So we don't update datasheets, we like to work with outdated ones (the documentation for 'updating' an datasheet is horrible).

Even more funny was that yes we release stuff, but the idea of releasing verified and examined material was never performed. If I looked in the workshop with past prototypes, lots of bodges and most of them were incorrect footprints or symbols. Classic mistakes. On my boards too, despite everything was verified and checked (as I was to believe). The ISO didn't help in that at all, it only gave extra paperwork and signing to do..

I hate it too. It can be useful, but then all procedures should be thought off clearly and also followed. ISO was required there because they wanted to manufacture high-tech and medical equipment, where it apparently is required or boosts sales ('confidence factor'), which I understand :)

Edit:
@GK; that's how it works. You know how ISO certification went at grad company? One guy looks at your procedures, your product(s) and other crap. To reduce 'audit' time, they decided it was a great idea to drive 70km to a restaurant in Amsterdam, spent 1.5 hours dinner there, and drive 70km back again. "There were no issues"
 Total lunch time: ~4 hours. Total audit time: ~2 hours. Now the day is 'over' (6 hours mate? Where do I sign?) and he left.  :o
« Last Edit: July 19, 2012, 11:28:45 pm by hans »
 

Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #72 on: July 19, 2012, 11:03:29 pm »
Very bad failure mode. It should fail with a fuse blown or 0V output. If they had a ~36V TVS on the output the worst case would be a blown fuse. But no... There's a reason I prefer an old surplus PSU to a new crappy one...
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #73 on: July 19, 2012, 11:33:00 pm »
Very bad failure mode. It should fail with a fuse blown or 0V output. If they had a ~36V TVS on the output the worst case would be a blown fuse. But no... There's a reason I prefer an old surplus PSU to a new crappy one...
http://the4thpin.comeze.com/2012/07/06/lodestar-8202-teardown-purchase-location-reveal/
I think you'll like this one ... it's from the 80's and in top order
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Offline madires

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #74 on: July 19, 2012, 11:33:45 pm »
Hi!

Official response from Korad (in part):

Quote
What you received was the early delivery and in this delivery, there is something wrong with those transistors. And we have improved since that shipment.

I'm reading: We messed up that batch, but didn't tell anyone and let the resellers sell the bad units. Bad luck for you if you got one of those. We fixed the problem and you may buy a new one (and help us making more money).

Cheers
 madires
 

Offline Scopeman1

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #75 on: July 19, 2012, 11:37:31 pm »
Can we stick to topic? ISO is polluting this thread.   There are exceptions to all rules and we all know situations when quality systems get in the way of a good product, right?  We designers are probably the most non-conforming and hopefully creative people on the planet, so of course we hate ISO or anything else that forces conformity.  It is for the boring people in the QA dept so that hopefully someone ends up with what we intended over and over again. If a company chooses to have a quality policy and have it audited then good for them. Any company's quality policy, ISO or not, is only as good as its processes, implementation and its mangers making sure it is followed. If your hot new product is depicted in a folder full of scribbles then whose fault is that? And in 5 years when it needs repair and the folder's gone missing, same thing.   So long as having a QA policy is not used for inflating prices then you are probably safer buying from a company that has an ISO9000 quality system than buying from one that has not. There will be of course exceptions.  So start a new thread for more ranting on ISO9000 and let's see how this PSU situation develops.  It sounds like they developed a 3A supply then pushed it to 5A with nothing more than a bigger transformer and it crapped out. 

Hmmm I suppose this post was mostly a bit off topic too....  must be a breakdown in the blog's QA system....

 

Offline Scopeman1

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #76 on: July 19, 2012, 11:50:14 pm »
To add to madires' comment.  If it was not for TRIO Smartcal's QA policy, they would still be selling it.  How many other Korad resellers round the world have seen this and have also taken it off sale until they know they have good ones?  Plus Dave can we have a comment from Trio Smartcal about what they will do about those they have sold already?
 

Offline free_electron

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #77 on: July 20, 2012, 12:46:33 am »
So there you go, under specced (or dodgy) transistors, surprise, surprise!  ::)
Genuine high power transistors are not cheap, and have been scammed on the grey market for
-gasp- surely a top quality brand like Korad would not have bought a lot of transistors from some shady chinese parts broker that sanded off the real manufacturer and put some other, more expensive part number on them?   ;D

As for ISO : there is nothing wrong with that. It is just a standard for traceability and process. But, and this is the key point : it does not define the actual process.. It only ensures you can track things. Yes it is a quality standard, one that measures the quality of the papertrail. I also prefer to but stuff from iso companies. You wont find any shady fake parts dealers there. And if you do, you will be able to track where the stuff came from and get your money back.

Now, as far as the hammering on calibration companies goes : i am not going to blast triocal here, i got no quarrel with them and do not know how they operate, but : i would assume that they would have tested these supplies under max volt, max load for 24 hours. Meaning: set the supply at 30 volts and pull 5 amps from it. Leave foer 24 hours. If no magic smoke escapes. Pass.
Since korad doesnt specify anything else like impulse behavior or load regulation.. Can't really verify..

In general ( again: i do not know triocal and have no quarrel with them ) , it is my experience that calibration companies only verify that a product falls within manufacturers specs. If korad only gives two numbers there is little to verify. If the manual lists a thousand numbers under different test conditions they will have a lot more work. So if this korad thing, with the meagre manual fries under some weird condition you can't blame triocal. There were no specs. Like dave said : safe operating area ? Unknown. It may very well be that you can only draw 5 ampere at 30 volt. Dial it down to just above the relay switchover and the thing may go outside of the soa as that is the point where the transistors burns off the most heat. Its got full voltage from transformer and lowest at output , not causing switching down of transformer. And then smoke comes out.... If this is not documented... Point finger at manu for not documenting this. The manu may be ISO, but if its not in there its not in there. There is a paper with specs, check , ISO stamp...

Second point. Most callabs ( i'm not fingering triocal, i dont know them. This is again just my experience) do not have the skill or know how to adjust a machine and bring it back into spec. It's pass or fail. Or they send it to the manufacturer for alignment. There is a lot of small callabs that do cal a multimeter for 50$ they also do a scope for 100$.. ???.. Really ?

Third point : some callabs jave no clue what they are doing. We got two power supplies rejected because they outputted -0.3 volt at 60 mA when the output was 'off'. I contested that and told them to read service note xyz of the manufacturer. For a particular range of serial numbers this was normal. This note was an addednum to the specs. Their answer was ' we can't know everything... I kicked them out. As a callab it is your job to know those things. How can you perform a verification if you don't know what you are verifying....

Fourth point: it is your job as user to read the manual of the machine you are using and know its limitations and specifications. Of course, if none are given your guess is as good as mine. Serious manufacturers will have calibration intervals given in the manual and the verification / adjustment procedures will be available, free / paying / or there will be a procedure to return it to the manu for calibration. If there is no procedure ,( either as a document , paying or free, or a statement it must be returned to manu ),  ... Run for the hills....
« Last Edit: July 20, 2012, 01:13:37 am by free_electron »
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Offline jpelczar

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #78 on: July 20, 2012, 01:07:29 am »
I guess one of the Murphy laws kicked in. Even if you think you test everything 100%, you'll find a bug/glitch one day after the product is in the shop ...


When finished he puts the folder down, smiles and says “very good, that all appears to be in order” and walks out of the workshop. We got our certification. To this day I’ve still not made up my mind if that guy was a complete nincompoop incapable of distinguishing a technical drawing from a recipe for black bean chicken, or if the managers had just bought him a really expensive lunch.

I think small "incentive" in the envelope was involved there ;-)
 

Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #79 on: July 20, 2012, 01:17:45 am »
I have a nice 30V 3A power supply by Tagasaki, quite old, not sure how old though, made in Japan.

Built like a brick and weighs as much as 100!
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #80 on: July 20, 2012, 05:12:00 am »
To add to madires' comment.  If it was not for TRIO Smartcal's QA policy, they would still be selling it.

It doesn't take a policy to make a business decision. And it doesn't require ISO. All it takes is the boss saying "We stop selling this for the moment".
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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #81 on: July 20, 2012, 09:57:46 am »
To add to madires' comment.  If it was not for TRIO Smartcal's QA policy, they would still be selling it.
Not really. QA policy would simply require you to document who you were selling the suspect batches too and when you did so. Trio withdrew the product from sale based on Dave's experience. That is an action to protect both themselves and potential customers.
All this second guessing and speculation about extensive test procedures that could have been, is fanciful stuff, devoid of commercial reality. You cannot economically or practically test for EVERY possible eventuality and you certainly cannot repeat that level of testing for every batch.
The problem with QA certification is in it's implementation. Pedantic regulation that has all too often replaced common sense practices with inappropriate compliance practices. The real tragedy is a national emphasis on QA with little or no recognition of the value of QC or common sense. Bow ties and bullshit at 30 paces, and a regulatory environment that impedes rather than assists industry.

From my point of view I'm glad that vendors like Trio Smartcal are prepared to put stuff forward for tear-downs and evaluation. I am also heartened that action was taken based upon the results.  There is no basis for universal condemnation of this or any product based upon a single review or incident. Sure you can find bulletproof gear but good luck finding it in the price bracket  where the Korad exists. What we have seen is a vendor who acted quickly and some response from a manufacturer.  Compare that with your mileage buying a similarly priced item off eBay from vendors you know little about. If the fault takes anything more than a fortnight to emerge you'll essentially be on your own.
Alternatively you could pay up to twice the price for a similar item from national parts chains. Why? Because they factor a proportional rate of failures, hand you a replacement and jettison the original in the nearest skip bin. Failure rate becomes too high they withdraw the line without notice. Good luck seeking long term support.

At it's price point I'd still consider a Korad from another batch, Dave's experience giving me a heads up on some possible failures. For a critical application I wouldn't have been considering something in this price bracket in the first place.

 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #82 on: July 20, 2012, 10:11:26 am »
SO I'm confused.  Was Dave's unit a pre-production model that has since been fixed?  Or is there a flaw in all of the units on the market?

Call me crazy but I'm still considering buy one, if I can just confirm that the issue has been fixed or not.

Offline cknight

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #83 on: July 20, 2012, 10:14:52 am »
I'm kind of curious about the apparently undocumented over-voltage and over-current buttons.  What do these buttons do exactly?  Are they enabling/disabling OCP and OVP?  And if so, what state were they in when the unit failed?   

It's also curious that sight unseen Korad is attributing it to a transistor.  It would seem to me that they must have been able to duplicate the failure or they already knew that the transistor is under-rated already.

Cheers,
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Offline ivan747

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EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #84 on: July 20, 2012, 10:38:41 am »
SO I'm confused.  Was Dave's unit a pre-production model that has since been fixed?  Or is there a flaw in all of the units on the market?

Call me crazy but I'm still considering buy one, if I can just confirm that the issue has been fixed or not.

Fair call. If you decide to buy one, remember to make a video!
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Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #85 on: July 20, 2012, 02:19:20 pm »
SO I'm confused.  Was Dave's unit a pre-production model that has since been fixed?  Or is there a flaw in all of the units on the market?

I think it was "early production", not pre-production. There is the real possibility some other suppliers may have got dud units too.

Quote
Call me crazy but I'm still considering buy one, if I can just confirm that the issue has been fixed or not.

Korad claim it is fixed and no one else will have the problem.
I believe them for future shipments, but I suspect that's not guaranteed for any previous shipments.

Dave.
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #86 on: July 20, 2012, 02:23:39 pm »
I'm kind of curious about the apparently undocumented over-voltage and over-current buttons.  What do these buttons do exactly?  Are they enabling/disabling OCP and OVP?  And if so, what state were they in when the unit failed?   

I believe you can see in the video that they were switched off.
Whether or not that means the unit is no longer protected from shorts or whatever, I have no idea, as we are not told how these modes work at all, or what the performance envelope the unit is actually designed for.

Quote
It's also curious that sight unseen Korad is attributing it to a transistor.  It would seem to me that they must have been able to duplicate the failure or they already knew that the transistor is under-rated already.

I get the sneaking suspicion that they may have already knew. But I could be wrong, they may have just investigated very quickly and it was an immediate "Doh!" moment. Like shipping the 3A board in the 5A unit or something like that?

Dave.
 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #87 on: July 20, 2012, 02:44:10 pm »
There is the real possibility some other suppliers may have got dud units too.


Hmmmm.  I wish there was someway to know before ordering (say from ebay or amazon, other than your supplier) if the problem has been corrected on those units.

And the problem is fixed, but it's still pulled off their site?  (scratches head)

« Last Edit: July 20, 2012, 03:35:41 pm by george graves »
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #88 on: July 20, 2012, 03:19:10 pm »
There is the real possibility some other suppliers may have got dud units too.

Quote

Hmmmm.  I wish there was someway to know before ordering (say from ebay or amazon, other than your ) if the problem has been corrected on those units.

And the problem is fixed, but it's still pulled off their site?  (scratches head)

I would not take Korad's statement too serious. For me it is a case of that they told people what they would like to hear, not what really happened. Something very typical in China. I would not be surprised if Korad didn't change anything in the past and has no intention of changing something in the future. The heatsink/fan combination on that thing is is so bodged, it might kill any transistor, bad batch or not.

But if they knew about it, if they still shipped the units, or not telling their retailers once they learned about it, you can extrapolate what their behavior will be next time there is an issue. A voluntary recall it won't be.

And the point with Trio Smartcal is, they opened it, they followed their process, but no one there said "uhm, that is not good enough". They wanted that thing. And if you start your evaluation from the point of view "we want it", or if your process is biased that way ("how can we accept things?", instead of "how can we protect ourself from junk?"), you end up taking such things on board. The reality is that maybe that these days no one, not even the Chinese can't make an acceptable $99 programmable PSU. 
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Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #90 on: July 20, 2012, 05:18:55 pm »
BAW... HK people have different mindsets than people from china
 

Online ejeffrey

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #91 on: July 20, 2012, 11:53:20 pm »
I'm kind of curious about the apparently undocumented over-voltage and over-current buttons.  What do these buttons do exactly?  Are they enabling/disabling OCP and OVP?  And if so, what state were they in when the unit failed?   

Probably the OCP and OVP are done in software.  That is, when the MCU detects an OV or OC condition, it turns off the output by setting the output to zero.  Since there is no separate turn-off relay or even a FET, once the main pass transistors blew out, they performed no function.
 

Offline TestBox

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #92 on: July 21, 2012, 12:38:29 am »
If someone who is simply bored at work and has nothing better to do than conjure up speculative crap about what the Chinese thought, did, will do etc when they don't have a shred of evidence to support their allegations, and would simply wait with the rest of us, then we'll get a true picture of what's going to happen here. Dave has a blown up unit. If a new board turns up with different transistors then we'll know the truth.  If it has the same transistors then we can draw our own conclusions. In the meantime Trio SmartCal has done the right thing by taking them off the market until it's sorted.  That seems reasonable to me.
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #93 on: July 21, 2012, 12:54:36 am »
If someone who is simply bored at work and has nothing better to do than conjure up speculative crap about what the Chinese thought,

You work for Trio, don't you? But anyhow, feel free to kiss my arse any time it is convenient for you.

Oh, and I deal regularly with Chinese companies and engineers. Bunch of liars, all of them.
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Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #94 on: July 21, 2012, 04:53:39 am »
Yup, mostly liars. BAW's right there.

No matter which nation, china or hongkong ( even koreans! Those d!cks! )

they lie.  :)
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #95 on: July 21, 2012, 10:06:46 am »
You work for Trio, don't you?
What part of that engineering degree did they devote to coming up with wild conclusions?

Quote
But anyhow, feel free to kiss my arse any time it is convenient for you.
While I'm not one to deny anyone from acting out their particular fetish. You do need to realise that 1) this should always be done a sufficient distance from livestock and 2) it is likely to result in your ending up with lipstick stains on the back of your head.  :)

Quote
Oh, and I deal regularly with Chinese companies and engineers. Bunch of liars, all of them.
I deal daily with Europeans, Yanks, Canadians, Asians, pasty Poms and fellow Aussies . As a competent engineer the only reasonable conclusion I can draw is that any generalisation s based upon races would range from flawed to plain ignorant. Was "racial stereotyping" included in that old school tie education of yours before or after they did "Wild Conclusions"?   ??? ;) :D
 

Offline TestBox

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #96 on: July 21, 2012, 12:27:36 pm »
Given Bored's rear-end fetish, we might have to check the dictionary for all meanings of "bored" to make sure we have the right one for why he really is "bored"@ work.  That then begs the question does he enjoy his job?

 

Offline PbFoot

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #97 on: July 21, 2012, 12:28:01 pm »
A friend of mine bought a cousin of the Korad unit - its a Quakko HY3005DP. Along with the infamous full output power for 1 second on power on, it has some other serious problems. I've taken apart the unit, and it does have significantly different construction internally when compared to the Korad.

He cooked his PS in almost the exact same conditions, and it exhibited almost exactly the same failure mode. ETA: (As the Korad did in Dave's video.)

I am sad to say I also have one of these HY3005DP, and it's a total pile of crap. I don't run it at high loads, so it still works, but next time I am getting an entry level Agilent.

-PbFoot
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #98 on: July 21, 2012, 01:10:31 pm »
I've taken apart the unit, and it does have significantly different construction internally when compared to the Korad.
We have seen this with lots of budget test equipment, the cases are sourced and/or cloned by a number of suppliers and assembled for different markets and budget extremes.
While units may look like a simple re-badge they be entirely different in construction and performance. It's another reason why you are always better to source budget stuff from known supply sources.
 

Offline Ed.Kloonk

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #99 on: July 21, 2012, 02:48:14 pm »
Unless you really need the programmability or the digital display, I think many people would do much better (at the same price) with an old tank of a power supply like this one:
http://www.ebay.com/itm/HP-6227B-Dual-DC-Power-Supply-W-Option-40-0-25V-0-2A-30-Day-WARRANTY-/300743973561?pt=LH_DefaultDomain_0&hash=item4605bcdab9

There will certainly be no funny business with it!

I fully agree. I own a 20 year old Altronics 50v (3-35v/5a) switchmode psu kit. It has two analogue meters on it that are connected right to it's output. Nice multiturn adj pot. No current limiting but it is sure nice to be able to glance over and see what's going down the wires.

The other remark I wanted to make is about the serial and usb connectors on the back of the power supply. On the back? Wouldn't you prefer then on the front panel?

I noticed that the input rating says 220v. I knew an electrician who had a fight with and air conditioner company whose machine was rated 220v and then claimed that it was not covered under warranty because it had been wired to Australian 240 volts.

I wonder if that is what happened to the psu. I saw that the tranny is rated 240, but you know the circuity in these cut-price gadgets isn't designed with a whole lot of plus/minus in mind.


hmmm. The thot plickens.




« Last Edit: July 21, 2012, 02:50:22 pm by Ed.Kloonk »
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #100 on: July 21, 2012, 03:55:50 pm »
I noticed that the input rating says 220v. I knew an electrician who had a fight with and air conditioner company whose machine was rated 220v and then claimed that it was not covered under warranty because it had been wired to Australian 240 volts.

Australia is not officially 240V any more. It's 230V
http://en.wikipedia.org/wiki/Mains_electricity_by_country

Dave.
 

Offline Ed.Kloonk

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #101 on: July 21, 2012, 04:00:21 pm »
I noticed that the input rating says 220v. I knew an electrician who had a fight with and air conditioner company whose machine was rated 220v and then claimed that it was not covered under warranty because it had been wired to Australian 240 volts.

Australia is not officially 240V any more. It's 230V
http://en.wikipedia.org/wiki/Mains_electricity_by_country

Dave.


Bastards. They just stole ten volts from me.

Give it back!

 

Online SeanB

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #102 on: July 21, 2012, 04:16:46 pm »
Ed, a lot of compressors are wound for 200V, as this saves copper in manufacture. Of course it will overheat........ But again most are connected with undersize cabling anyway, so it evens out, warmer wire and cooler windings. Note that they are still marked 220v in this case.
 

Online IanB

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #103 on: July 21, 2012, 04:22:11 pm »
Australia is not officially 240V any more. It's 230V
http://en.wikipedia.org/wiki/Mains_electricity_by_country

Dave.

You should definitely measure the actual voltage at your mains sockets and see what the meter says. My guess is that if the system was originally designed for 240 V then it is still 240 V. It is a huge cost to change installed infrastructure to a different specification. It is much cheaper to change the voltage on paper by adjusting the allowable tolerance.
I'm not an EE--what am I doing here?
 

Offline David_AVD

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #104 on: July 21, 2012, 04:38:51 pm »
Yes, when we changed to the 230V standard it was only on paper.  Just the tolerance was changed.  I still measure 240V - 245V at the socket.
 

Offline HackedFridgeMagnet

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #105 on: July 21, 2012, 05:02:03 pm »
One point I'd like to make is that Trio Smartcal's ISO:9 whatever accreditation didn't prevent them from selling what seems to be a bit of dodgy junk, one that fails and could possibly damage whatever it is attached to.
I don't know how this PSU could come under the banner of quality assured. Not when the manufacturers details are sanded off half the chips.

I don't suppose Trio Smartcal is going to publish the relevant parts of their QA manual. So we can be sure they followed it when they decided to put this PSU in their range.
If  Trio Smartcal were interested in assuring quality, they should put into their QA manual, "Dont sell equipment that contains chips that have their details sanded off."

ps. I don't think Trio should actually do this, they should just skirt around the QA stuff like we all do.
After all ISO QA accreditation is just a sales tool, one that lets you sell to Government and big companies, and helps keep small companies out.
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #106 on: July 21, 2012, 05:30:45 pm »
Things have certainly been getting interesting.  More questions to answer and here's a bit of an update.

1. What are doing about those we have sold?
 - We are already contacting the customers to advise them of the issue. They can have a full refund, or if the unit has survived Dave's treatment after modification, they can have their unit modified and returned.  Korad has told us they are sending enough parts to modify all the remaining supplies we have in stock and those we have already sold.

2. What if it fails after modification?
- If it fails after whatever modification we need to do, then we will give customers their money back , or exchange for another brand at a preferential price on a case by case basis.  We will then have a totally different discussion with Korad.

3. The transformer Rating?  - It is rated 240V.  We had delivery delays because Korad only had 220V trannies when we first ordered. I suspect they didn't think of changing the sticker on the back.

4. Connections for USB and RS232 on front or rear?   I suspect if someone is hooking this up to a PC they don't want a serial or USB cable coming out the front as well as the supply leads and getting mixed up in the bench spaghetti.  The USB is for PC connection not a memory stick so if it is rack-mounted or on a shelf above the bench, it is probably better on the rear panel. But that's a simple matter of personal preference ultimately.

5. Someone else mentioned the ATTEN APS3003S-3D 
- This is a triple output supply and we sell truck loads of them.  They sell for $249+gst off our website.   Compare that to what you get from the big nationals.  We offer it with a 2yr warranty. We have sold several hundred of them with with just one warranty claim. It is a good supply for the money. And it's a linear. And heavy!    http://triosmartcal.com.au/dc-bench-supplies/2432-atten-aps3003s-3d-dual-power-supply-0-30v-3a.html

6. Uncle Vernon is very correct in pointing out this forum is not a place for racial stereo-typing. We also deal with multiple suppliers from USA, Europe and Asia and we have had no real problems so far.  Dealing directly with manufacturers is OK. They are looking for a long term relationships so you help grow their business and in my experience all those we have dealt with have been fine. It also comes down in the longer term to dealing with companies that you trust and the proof is when something goes wrong, as it has here.  Trust is something that builds with experience and Korad is a new supplier for us, so we need to see how things develop.

So far Korad has been responsive, Dave is copied on emails between us and Korad so he can back me up if he chooses. 

7. Whether Korad knew of the problem when they shipped to us is another issue, and if they found out later there was a batch issue, then leaving the problem for the distributor to find is not the best policy. Also it would depend when they found out be it last week, month, several months ago,  I don't know the answer. But I do need to know.  I have also asked for serial numbers of affected units. 

8.  The sample we tried in our lab was from a different batch to the production units we have in stock. Dave does not have the sample we tested. That is in my garage, works fine, I use it for a quick charge on my boat battery and it comes in very handy.  Dave tested an early production unit, hence my concern and the immediate withdrawal of the product from sale.

9. Why did we take it on in the first place?
Their products looked good on paper offering a good performance at a very reasonable price and down into the education market level and hobbist level. These PSU's  filled a hole in our portfolio for a low-cost programmable supply and as one we tested met it specs we gave it a go.  As I mentioned in an earlier post I have no problem submitting anything we sell for Dave to evaluate. If Dave finds something we don't then that's good for everyone.  How this Korad situation now develops remains to be seen. I will certainly keep this thread posted with developments.  We are just as intrigued as you are!!  Korad's true business ethic and customer care will certainly come out now.  If they do not rectify the situation then they are gone from our range and we take back those we have sold offering the remedies above. It's that simple.

10.  Someone else mentioned that the next supply they buy will be a low cost Agilent. Well I'll declare my bias as Agilent's biggest distributor in Aussieland and say that I totally agree.  We sell Agilent bench supplies at less than Agilent's list price.  That means they start price from us at just $336 +gst. See here :
http://triosmartcal.com.au/1571-agilent-u8001a-dc-power-supply-30v-3a.html

For those in the market for one now, Agilent has an great offer on the E36xx series of bench supplies.   If you buy a qualifying power supply from their E36xxA range for upwards of about $530 +gst they (we) will give you a U1272A multimeter for free. The meter sells for about $440 including gst.

http://triosmartcal.com.au/2251-agilent-u1272a-dmm-digit-water-dust-resist.html

Click on the banner here to see the offer.  www.triosmartcal.com.au 

11. If anyone has further questions about this Korad situation and you can't wait for a post to be answered, then why not just drop me a PM. It goes straight through to my in-box at work. If I have the answer then I'll let you know, and if relevant to the others following this thread then I'll post it, otherwise if I don't know I'll try to find out.

12. Just measured the voltage from the mains here in Castle Hill.  It was 244.1V

13. We don't check for chips with the lettering removed. I think this is were a grasp of reality helps. Why would you check for chip lettering on a $199 supply?  To troubleshoot to component level is just not worth it. Companies remove lettering to protect their IP and  big multi-nationals are doing exactly the same. Sure it pisses off geeks who want to know what the chip is, but is that why you buy something? Because the writing is still on the chips?  Most don't.

14. HackedFridgeMagnet thinks that ISO:9xxx  could have stopped this getting into our range. Absolutely not. Look at Dave's first reaction to the product. Even during the tear-down. It came out OK for a $199 supply. In fact the review was going well until it failed. Now that it has failed when it shouldn't have failed is when QA really kicks in, and remember as someone else said, wrapping your head in tin-foil and singing Hare-Khrishna could be in your QA process but it has to be relevant. What has happened here since the failure is relevant the failure was recorded and appropriate action taken. No tin-foil harmed in the process.  As for this comment QUOTE "ps. I don't think Trio should actually do this, they should just skirt around the QA stuff like we all do." ...........  You must work for one of our competitors  ;-)

15. Finally for David_AVD who did a very relevant post in the ShoutBox  QUOTE:  "Some People want the cheapest price and the best service / warranty. It doesn't usually work that way" END QUOTE.  Well that's the challenge we all face as sales and service companies. We want to do just that to have a competitive edge.  Again as stated earlier it comes down to you getting what you pay for so long as you are not being ripped-off which includes after-sales support & service..  It is all a balancing act that we have to perform with the variables in the value equation.

Cheers & keep it coming.
« Last Edit: July 21, 2012, 05:41:36 pm by TRIO_Smartcal »
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Offline Ed.Kloonk

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #107 on: July 21, 2012, 05:47:12 pm »
@TRIO_Smartcal

I commend you for having the balls to do what you are doing and for being bold to hand the gadget to Dave, the hardest, most critical in the biz. Good on you.

Don't let them there knockers knock you!

 :)
 

Offline David_AVD

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #108 on: July 21, 2012, 05:50:20 pm »
Nice reply.  TRIO Smartcal seem to be doing exactly what I'd expect any decent company to do.

Local support and warranty is often undervalued.  I buy some (usually very low cost) items direct from overseas and when I do, I accept that I am taking a calculated risk in doing so. (in regard to warranty, represented specs or even receiving the item!)

I must admit my fist reaction was to give the Korad unit a miss after Dave's unit went belly up.  Now I'm quite prepared to consider it if the issues are sorted and TRIO Smartcal offer it for sale.  I'm damn glad I didn't jump in for the slightly cheaper option of buying in from USA and having no support.

As for the sanded chips, I accept that's what some manufacturers do.  It only annoys me slightly as a failure of that part would usually mean I'd just buy another unit anyway.

It has to be remembered that this is a low cost power supply.  Much cheaper than any of the other programmable units I've seen.  The way some people are going on you'd think it was a very expensive high end product!  It's all horses for courses folks.
 

Online SeanB

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #109 on: July 21, 2012, 05:53:38 pm »
Add to this there are a lot of residential areas where there are feed in solar supplies where the mains voltage during the day is 260V or more, as the voltage compensation from the supplier is not meant to work the other way and get power fed from the load side.
 

Offline Ed.Kloonk

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #110 on: July 21, 2012, 05:54:20 pm »
Nice reply.  TRIO Smartcal seem to be doing exactly what I'd expect any decent company to do.

Local support and warranty is often undervalued.  I buy some (usually very low cost) items direct from overseas and when I do, I accept that I am taking a calculated risk in doing so. (in regard to warranty, represented specs or even receiving the item!)

I must admit my fist reaction was to give the Korad unit a miss after Dave's unit went belly up.  Now I'm quite prepared to consider it if the issues are sorted and TRIO Smartcal offer it for sale.  I'm damn glad I didn't jump in for the slightly cheaper option of buying in from USA and having no support.

As for the sanded chips, I accept that's what some manufacturers do.  It only annoys me slightly as a failure of that part would usually mean I'd just buy another unit anyway.

It has to be remembered that this is a low cost power supply.  Much cheaper than any of the other programmable units I've seen.  The way some people are going on you'd think it was a very expensive high end product!  It's all horses for courses folks.

This is why I don't understand why Gerry Harvey got nailed when he went after Ebay. He for some reason forget to ram home the point about local service that we all enjoy but sure miss when we bypass it.  :-\
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #111 on: July 21, 2012, 06:08:43 pm »
This is why I don't understand why Gerry Harvey got nailed when he went after Ebay. He for some reason forget to ram home the point about local service that we all enjoy but sure miss when we bypass it.  :-\

Perhaps because of HN and other discount appliers (generally illegal) attitude towards warranty and customer support. Once that card is swiped they don't want to know you. The expectation being you should seek out the manufacturers service company. The established retailers just don't get it. Which is why they are losing out to online retailers. Often times you can be better looked after by an online vendor.

The vendors that support their products, who provide price and specifications online and those who are prepared to interact with new media are the ones who will benefit and grow.
 

Offline HackedFridgeMagnet

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #112 on: July 21, 2012, 06:22:11 pm »
Quote
13. We don't check for chips with the lettering removed. I think this is were a grasp of reality helps. Why would you check for chip lettering on a $199 supply?  To troubleshoot to component level is just not worth it. Companies remove lettering to protect their IP and  big multi-nationals are doing exactly the same. Sure it pisses off geeks who want to know what the chip is, but is that why you buy something? Because the writing is still on the chips?  Most don't.

14. HackedFridgeMagnet thinks that ISO:9xxx  could have stopped this getting into our range. Absolutely not. Look at Dave's first reaction to the product. Even during the tear-down. It came out OK for a $199 supply. In fact the review was going well until it failed. Now that it has failed when it shouldn't have failed is when QA really kicks in, and remember as someone else said, wrapping your head in tin-foil and singing Hare-Khrishna could be in your QA process but it has to be relevant. What has happened here since the failure is relevant the failure was recorded and appropriate action taken. No tin-foil harmed in the process.  As for this comment QUOTE "ps. I don't think Trio should actually do this, they should just skirt around the QA stuff like we all do." ...........  You must work for one of our competitors  ;-)

Ps. I am a reluctant calibration customer, not a competitor.
Just so people are clear, I am not knocking Trio Smartcal or the the way you are handling this situation. I have to say you are going to lengths that I can't remember any distributor ever going. Well done, may it continue.
I am also not knocking you for selling inexpensive stuff rather than just the name brands. Sometimes it's every bit as good.

But I am knocking the QA accreditation system and the way sales people use it to imply that Quality is Assured when it is clearly not, because you don't know who made the chips, when they were made or even what they are. Do you even know if they are Pb free. If so how?

And I would be interested to know what your QA manual does say about how you check equipment before you sell it. Though I guess you will have to 'skirt around' answering this one. I can understand though.


 

Offline amyk

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #113 on: July 21, 2012, 09:46:15 pm »
After rewatching the review it looks like more than just the power transistors failed; why would it switch to the 56V tap when the preset voltage was far lower? I'd think that a good control loop would notice the abnormally high output voltage and go to the lowest tap, then maybe even detect that the voltage is still too high and shut off completely at the relays.

56V also looks a bit high for a supply that's rated for only 30V.
 

Offline madires

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #114 on: July 21, 2012, 10:48:38 pm »
A friend of mine bought a cousin of the Korad unit - its a Quakko HY3005DP. Along with the infamous full output power for 1 second on power on, it has some other serious problems. I've taken apart the unit, and it does have significantly different construction internally when compared to the Korad.

He cooked his PS in almost the exact same conditions, and it exhibited almost exactly the same failure mode. ETA: (As the Korad did in Dave's video.)

I am sad to say I also have one of these HY3005DP, and it's a total pile of crap. I don't run it at high loads, so it still works, but next time I am getting an entry level Agilent.
-PbFoot

Please read http://blog.mastechpowersupplies.com/ (top entry)

The special feature for pre-setting the current limit is absolutely gorgeous :-)))

Cheers

 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #115 on: July 22, 2012, 04:22:00 am »
After rewatching the review it looks like more than just the power transistors failed; why would it switch to the 56V tap when the preset voltage was far lower? I'd think that a good control loop would notice the abnormally high output voltage and go to the lowest tap, then maybe even detect that the voltage is still too high and shut off completely at the relays.

56V also looks a bit high for a supply that's rated for only 30V.
Maybe the relays failed and switched in all 3 taps? All did the transistors go short and recieved all 3 taps
It does sound like there's 15-15-0-15-15 to me
Dave, how many taps are there on the PSU?
 

Offline amspire

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #116 on: July 22, 2012, 11:31:14 am »
But I am knocking the QA accreditation system and the way sales people use it to imply that Quality is Assured when it is clearly not, because you don't know who made the chips, when they were made or even what they are. Do you even know if they are Pb free. If so how?
It is not up to QA to second guess the designers.

It is up to QA to act when an issue of quality arises, which Trio Smartcal have done pretty brilliantly.

It is not just the cheap Chinese products that have batch problems. I own a bunch of  HP 49G calculators thanks to a major batch problem that HP had. They had a batch of leaky capacitors that they used to back up memory as you change the batteries, and the result was the calculators wouldn't turn on. Change the capacitor and they work perfectly. To my knowledge, this problem affected just about every calculator using this batch of capacitors.

Are you suggesting that no-one should sell HP calculators?

Batch component problems happen in manufacturing, and the important thing is the response of the manufacturers and suppliers to this problem. It can happen to any manufacturer using components from any supplier.

It could be that this Korad supply has a design problem, and the correct response from QA is to to see that either the problem is fixed, or to recommend the product be dropped.

Do you have any problem in the way Trio Smartcal have responded?

I have never heard of any QA department of a distributor requiring that a third party manufacturer detail the source and date of manufacturing of every component in a piece of equipment that they make.

Richard.
« Last Edit: July 22, 2012, 11:39:00 am by amspire »
 

Offline jeremy

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #117 on: July 22, 2012, 05:47:03 pm »
Just putting it out there, but I want one. Two actually. Looks like a nice unit for small automation tasks. Hoping to hear from the guys at trio soon.

PS: stuff goes wrong guys. No-one is immune, not even NASA: http://articles.cnn.com/1999-09-30/tech/9909_30_mars.metric.02_1_climate-orbiter-spacecraft-team-metric-system?_s=PM:TECH
If Korad (and by extension, Trio) are going to fix it, then I'm happy. You'd get the exact same treatment if your 9000 series Agilent scope popped.
 

Offline HackedFridgeMagnet

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #118 on: July 22, 2012, 10:04:58 pm »
Quote
It is up to QA to act when an issue of quality arises
I was under the impression that Quality Assurance is about preventing these issues arising.
If they do arise then it is about preventing them from arising again.
These are lofty goals, and I subscribe to them, but my experience of ISO:9000etc is that it doesn't necessarily assure anything except a lot of ticked boxes.

 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #119 on: July 22, 2012, 10:12:47 pm »
Quote
It is up to QA to act when an issue of quality arises
I was under the impression that Quality Assurance is about preventing these issues arising.
No it's about tracking and managing process so action can be taken when events arise. The word Quality should never appear in the title.
Sadly however more often than not QA is used as a blunt instrument to restrict or price out emerging competitor. It is also a tool for government authorities, insurance companies and large corporations to duck-shove blame and avoid accountability.

The we have lots of folders full of stuff so it can't possibly our error syndrome. Like throwing buckets of money, a short time- frame and some unrealistic expectations at an industry, while remaining three steps removed from the people who do the work. Then when all the roof batts catch fire and people start getting electrocuted you can blame fly by night contractors and obfuscate yourself from any responsibility. Worked for Kev, Pete & Julia.
« Last Edit: July 22, 2012, 10:18:15 pm by Uncle Vernon »
 

Offline amspire

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #120 on: July 22, 2012, 10:17:11 pm »
Quote
It is up to QA to act when an issue of quality arises
I was under the impression that Quality Assurance is about preventing these issues arising.
I do not think the QA department is meant to be capable of magic, or predicting the future.
Quote
If they do arise then it is about preventing them from arising again.
Trio Smartcal removed the supply from their catalog until the problem is identified and sorted. Then they will probably decide whether to sell it again or not. It sounds to me like they have done everything possible to prevent the problem happening again
Quote
These are lofty goals, and I subscribe to them, but my experience of ISO:9000etc is that it doesn't necessarily assure anything except a lot of ticked boxes.
ISO9001 is just a standard that makes you define the quality assurance procedures in your company, and ensures you follow your own procedures. You tick boxes if the QA procedures that you defined require you to tick boxes. If you have to tick boxes, you cannot blame ISO9001.

When you are assessed to see if you meet the 9001 standard, they check that your company is following the QA manual that you wrote for the company.

The procedures are as good or as bad as you make them. When a company like Trio Smartcal advertise that they are 9001 qualified, it indicates the company has written QA procedures, and that customers can expect the procedures are followed. This is important for customers like government departments.

Richard.
« Last Edit: July 22, 2012, 10:28:31 pm by amspire »
 

Offline HackedFridgeMagnet

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #121 on: July 22, 2012, 10:59:26 pm »
Quote
The procedures are as good or as bad as you make them. When a company like Trio Smartcal advertise that they are 9001 qualified, it indicates the company has written QA procedures, and that customers can expect the procedures are followed. This is important for customers like government departments.

Well now I am confused,
They have written procedures, apparently about QA but possibly not about the quality or the testing of the equipment they sell.
The procedures are about how they react if an issue of quality comes up.
I am supposed to trust them to carry out these procedures because they are accredited. Fair enough, but still they write these procedures themselves so I don't know what they are unless they tell me.
I don't feel much safer.

Sorry for being disingenuous Richard, but I feel you are too.
Quote
I do not think the QA department is meant to be capable of magic, or predicting the future.
Testing equipment before selling it is quite common.
Documenting these test procedures is also quite common.
Using these tests to estimate failure is quite common.
The fact that these tests are apparently not part of Quality Assurance is news to me, but I am not QA expert.
I did not mention magic.


I think you missed this part of one of my posts Richard.
Quote
Just so people are clear, I am not knocking Trio Smartcal or the the way you are handling this situation. I have to say you are going to lengths that I can't remember any distributor ever going. Well done, may it continue.

 

Offline taemun

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #122 on: July 22, 2012, 11:50:42 pm »
The test with the constant load of 50W where output was dropping to 0.2 volts was understandable at the electronic load would present an almost dead short when the supply output was switched on. A better test is to use the load switch on the dummy load to turn the constant power load on and off. This way the electronic load sees the set supply voltage and only switches in the appropriate current load for the power setting.

I think this was mostly overlooked, and (to my mind) is the correct interpretation of *that* 'fault'. Constant wattage is pretty much useless for switch on testing.

I groaned when I saw the teardown, the overall internal build was very reminiscent of my Jaycar MP3087. That unit has no fan, and badly needs one when powering a high current load - a 100W LED will make the output transistors untenably hot in a relatively short period. Also, its regulation was so poor that you could visibly see the current (in CC; or voltage in CV) ripple in the LED's light output.

[Edit: in particular, I noticed the chassis had the same dodgy roof rails which didn't meet the front panel at a right angle.]

On the other hand, I can't say enough good things about Agilent 6632B's. A few of them fell into my lap a year ago. They can source or sink 20V/5A (yes, it'll sink full rated power). Sinking is incredibly useful, as is the 20mA (1uA resolution) current sense mode, when dealing with small project power supplies. Testing switch-mode PSU efficiency couldn't be easier.

The 6632B fan is noticeable, and entirely current load based, but these are really designed for rack-mount use, and I doubt that most folks care how much noise their equipment rack makes - it means the units stay cooler and hence last longer.

Considering that you can buy that Korad for $US 75 on AliExpress (plus postage), I wouldn't expect anything good to come from them. Sticking "Lab Grade" on a product doesn't make it so.
« Last Edit: July 22, 2012, 11:56:37 pm by taemun »
 

Offline nixxon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #123 on: July 23, 2012, 01:53:23 am »
"Considering that you can buy that Korad for $US 75 on AliExpress (plus postage), I wouldn't expect anything good to come from them. Sticking "Lab Grade" on a product doesn't make it so."


I have only seen the D and not the P(rogrammable) version at AliExpress...

nixxon @ iPhone in Ste.Maxime, France at the moment...
 

Offline amspire

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #124 on: July 23, 2012, 02:26:27 am »
Testing equipment before selling it is quite common.
Documenting these test procedures is also quite common.
Using these tests to estimate failure is quite common.
The fact that these tests are apparently not part of Quality Assurance is news to me, but I am not QA expert.
They did test the supply before offering it for sale, and their test supply worked. How can you estimate failure when the supply does not fail in tests?  It is a very cheap programmable supply, so they would not expect it to be a top quality design and build.

The unit Dave got was from a different batch, and it was working for most of Dave's review. It was not faulty initially. It failed while Dave was testing.

Quote
I think you missed this part of one of my posts Richard.
Quote
Just so people are clear, I am not knocking Trio Smartcal or the the way you are handling this situation. I have to say you are going to lengths that I can't remember any distributor ever going. Well done, may it continue.
If you are not knocking Trio Smartcal's QA, what on earth have you been whinging about?

Even for the manufacturer, QA and QC (quality control) are two completely different things, and I think you think they are the same. Do you understand that a company with the highest QA standards can choose to sell a cheap low quality product without any conflict of the QA standards?

Lets get back to basics.

One power supply has failed. The supplier has taken appropriate action. A big tick for the supplier. It appears the manufacturer has been communicating with the supplier and seems to be taking appropriate action. So so far, a tick for the manufacturer.

Failures exactly like this can happen with any company and with products of any price.

Let's acknowledge everyone who has done the right thing, let's see what happens, and just move on. There are people in this forum wanting to see if the manufacturer can resolve the problems, as they see the supply as something very useful at the price, even if it is a cheaper construction, and even if the boards are not cleaned as well as they could be.

Richard.
« Last Edit: July 23, 2012, 11:42:39 am by amspire »
 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #125 on: July 23, 2012, 10:23:59 am »
I think I'm going to go ahead and buy one.  It seems you can get one in the US for $100 shipped - with a 2 year warranty.  Even if it lasts 2 years and 1 day, then blows up, that's still a heck of a deal, and should suit me just fine.  There is very few times I need more than 1 amp - so in my case, it should see very light use. 

I'm just so impressed with the accuracy of the displays, and the controls.  It seems like a +$300 PS for $100.

There were a few people stating "well, see, you can't make a decent programmable PS for $100! - Told ya!" - well, why not?  It's a transformer, a case, some LED's and a hand full of other parts.  I don't see why not.

I'd like to buy something that is a bit more "industry standard" - but in a pinch, this will do nicely.  And in two years, I'm sure I'll have added a lot more equipment to my lab.

My 2 cents.

Offline HackedFridgeMagnet

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #126 on: July 23, 2012, 02:25:45 pm »
I did a quick search on QA vs QC and this was the first site found. They even have a picture.
http://www.iso9001consultant.com.au/QA.html
Quote
Quality Control does not ensure quality, it only finds instances where quality is missing.  Obviously it's better than nothing, but it has its limitations.  The most important of these is that you only find out that things aren't OK at the end of the process.

Quality Assurance developed from the realisation that quality could be improved by looking 'further up the line'.  It is aimed at preventing nonconformities/defects.

QA still has QC at its core to control the quality of service/product, but it goes beyond mere testing or inspection to also consider related activities or processes (such as training, document control and audits) that may be resulting in defects further down the line.   
I dont know if it's right or wrong but it is not consistent with what you say.

Quote
If you are not knocking Trio Smartcal's QA, what on earth have you been whinging about?
The nub of what I have been trying to say is that a company having QA accreditation doesn't assure me personally of anything.
The psu failing only reinforced this view.
Whereas the brand name Trio Smartcal does give me reason to feel assured, because I have heard of them, have dealt with them and know of others that do the same.
 

Offline taemun

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #127 on: July 23, 2012, 05:14:59 pm »
"Considering that you can buy that Korad for $US 75 on AliExpress (plus postage), I wouldn't expect anything good to come from them. Sticking "Lab Grade" on a product doesn't make it so."

I have only seen the D and not the P(rogrammable) version at AliExpress...

Apologies, I didn't notice the D suffix as opposed with the P suffix. My point still stands though, that isn't $100 worth of isolated USB/RS232 board.
 

Offline amspire

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #128 on: July 23, 2012, 05:36:32 pm »
I did a quick search on QA vs QC and this was the first site found. They even have a picture.

What that graph is not explaining is that QA is about defining and managing the processes in a company, not the quality of products. As QC is a subset of the processes in a company, it is under the QA, but the QA processes are only concerned that your QC is running in a proper way. A manager in the company defines how QC should operate, and then QA ensures that these rules are followed.  QA is about defining comprehensive processes and rigorously following these processes, rather then making it up as you go along. So if a product fails, rather then a manager saying "What will I do now?", people look up the QA manual to see what steps have to be taken, and they follow the steps. QC is only shown as part of QA in the same way that every other process in the company will become part of QA.
Quote
Quote
Quality Control does not ensure quality, it only finds instances where quality is missing.  Obviously it's better than nothing, but it has its limitations.  The most important of these is that you only find out that things aren't OK at the end of the process.

Quality Assurance developed from the realisation that quality could be improved by looking 'further up the line'.  It is aimed at preventing nonconformities/defects.

QA still has QC at its core to control the quality of service/product, but it goes beyond mere testing or inspection to also consider related activities or processes (such as training, document control and audits) that may be resulting in defects further down the line.   
I dont know if it's right or wrong but it is not consistent with what you say.
It is consistant if you understand what I have been saying. QA means you are dealing with a company that will handle complaints in a standard manner. You are not at the mercy of the mood of the representative you are talking to. Dealing with company with good QA standards is a good thing, but not in the way that I think you want.

I think you want a quality product.

QA does not care less about the quality of a product unless the company has written rules defining a process to determine the quality of a product. Once there are rules, then ISO9001 QA requires that the rules are followed, and if they are not followed properly, a non-conformance report must be raised within the company. This non-conformance report must then be acted on in some way - it cannot be ignored. If the independent ISO9001 inspectors see there are non-conformance reports that have not been addressed, they can suspend the company's ISO9001 accreditation.
Quote

Quote
If you are not knocking Trio Smartcal's QA, what on earth have you been whinging about?
The nub of what I have been trying to say is that a company having QA accreditation doesn't assure me personally of anything.
The psu failing only reinforced this view.
Whereas the brand name Trio Smartcal does give me reason to feel assured, because I have heard of them, have dealt with them and know of others that do the same.
It does not assure you that a product the company is selling is high quality. If they are selling a low quality product, you get a low quailty product, and that is totally fine with a good QA system.

However, a good QA process is important when companies have to cooperate as it means that the QA processes of the 2 companies can be set up to work together efficiently. A big reason Trio Smartcal has ISO9001 is because many other potential clients, particularly governmental organisations, require they have ISO9001. These customers will not do business otherwise. That is why the ISO9001 compliance is advertised.

Richard.
« Last Edit: July 23, 2012, 06:20:49 pm by amspire »
 

Offline Galenbo

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #129 on: July 23, 2012, 07:00:46 pm »
...
It does not assure you that a product the company is selling is high quality. If they are selling a low quality product, you get a low quailty product, and that is totally fine with a good QA system.
...

And even, to produce absolute CRAP products, you need good machines and a good Quality control,
when not, you'll not be able to produce CRAP in high volumes
If you try and take a cat apart to see how it works, the first thing you have on your hands is a nonworking cat.
 

Offline HackedFridgeMagnet

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #130 on: July 23, 2012, 07:49:58 pm »
I don't wont to think about Crap in high volumes, it's dinner time.

You're probably right, Richard
But from personal experience, I see a red flag when people mention QA accreditation.
I'll leave there.
 

Offline MBY

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #131 on: July 25, 2012, 07:13:59 pm »
After rewatching the review it looks like more than just the power transistors failed; why would it switch to the 56V tap when the preset voltage was far lower? I'd think that a good control loop would notice the abnormally high output voltage and go to the lowest tap, then maybe even detect that the voltage is still too high and shut off completely at the relays.

56V also looks a bit high for a supply that's rated for only 30V.
Exactly my thought! It's a bit confusing when we have two "contemporary" threads about the PSU. In the thread http://www.eevblog.com/forum/product-reviews-photos-and-discussion/korad-ka3005d-$90usd-30v-5a-dc-programmable-ps/ I was also rising the concern that it not make real sense to assert that the transistors where the only thing failing.

As you said, the control loop should switch in the right taps for the right setpoint not matter the actual voltage. Maybe the control loop broke and put those transistors out of SOA. The transistor failing may be the effect, not the cause. It could be something as easy as a bad solder joint, especially if the schematics of the relays are dumb so non energized relays switch in the highest tap, not the lowest.

Btw, I agree with Scopeman1 - lets keep the QA and ISO stuff outside the thread. The electronics is more exciting. 
 

Offline itdontgo

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #132 on: July 25, 2012, 10:40:50 pm »
I know that beeper sound, it's using a beeper that requires the micro to generate the tone. (They're cheaper than beeper with internal tone generators)

When you try and generate the ~2kHz by setting/clearing the mcu output pin in software other interrupts will semi-randomly delay the set/clear commands and you get a sound that's dirty like that.

To avoid it they need to use the dedicated hardware timer output pin on the mcu so the tone generation happens independently.
(or a beeper that does the tone generation itself)

This can be useful when you play a melody through a piezo.  If you use a PWM the perfect square ware sounds louder and quieter around resonance.  The dirty software interupt driven output plays at a more constant volume!

Offline itdontgo

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #133 on: July 25, 2012, 10:42:30 pm »
Someone at Korad has been found out.

Offline LEECH666

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #134 on: July 27, 2012, 10:45:56 pm »
*Sigh* Why don't they offer that Agilten 36xx PSU + Free Multimeter deal in Euroland? I really would considder buying, but shipping cost + custom taxes would really take the fun out of such a deal.

:(
 

Offline MickM

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #135 on: August 06, 2012, 12:00:48 pm »
Hi;
  is there any update on this?
Was the problem found?

Mick M
 

Offline MBY

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #136 on: August 08, 2012, 05:45:20 pm »
I'm also looking for updates. Anybody has any news?
 

Offline TestBox

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #137 on: August 27, 2012, 11:54:47 pm »
According to Trio Smartcal there is a delay at Korad's factory. I got the impression Trio Smartcal was not very happy with Korad. Neither would I be if something dragged on this long. Apparently the parts to rectify the problem were supposed to be shipped weeks ago but Trio is still waiting.  Knowing the Chinese they'll be waiting a very long time.  Glad I didn't buy one from overseas.   :P
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #138 on: August 28, 2012, 12:00:30 am »
According to Trio Smartcal there is a delay at Korad's factory. I got the impression Trio Smartcal was not very happy with Korad. Neither would I be if something dragged on this long. Apparently the parts to rectify the problem were supposed to be shipped weeks ago but Trio is still waiting.  Knowing the Chinese they'll be waiting a very long time.  Glad I didn't buy one from overseas.   :P

Korad have said they were moving office location which has caused the delays.

Dave.
 

Offline GEuser

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #139 on: August 28, 2012, 03:14:37 pm »
Mr EEVblog , what is that bendy thing on the bench on the right in the video , a light?

cheers , Paul .
Soon
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #140 on: August 28, 2012, 05:13:44 pm »
Mr EEVblog , what is that bendy thing on the bench on the right in the video , a light?

cheers , Paul .

His brand new mantis elite microscope
 

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #141 on: August 28, 2012, 05:17:26 pm »
Mr EEVblog , what is that bendy thing on the bench on the right in the video , a light?

cheers , Paul .

His elbow?
 

Offline GEuser

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #142 on: August 28, 2012, 10:46:40 pm »
Thanks very much T4P , great gizmo and "i love the smell of mantis in the mornings"  ;D

@UV , LOL

cheers....
Soon
 

Offline ProBang

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #143 on: October 29, 2012, 05:17:26 am »
Hello

According to Trio Smartcal there is a delay at Korad's factory. I got the impression Trio Smartcal was not very happy with Korad. Neither would I be if something dragged on this long. Apparently the parts to rectify the problem were supposed to be shipped weeks ago but Trio is still waiting.  Knowing the Chinese they'll be waiting a very long time.  Glad I didn't buy one from overseas.   :P

Korad have said they were moving office location which has caused the delays.

Dave.


Yeah, that's two month ago. IMO enough time to establish business as usual.
Once more:

I'm also looking for updates.
Is there any update on this?
Was the problem found?
Anybody has any news?

Greetings,


Hartmut
If you think my english is bad...
- then should you read my french!
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #144 on: October 29, 2012, 08:40:50 am »
Yeah, that's two month ago. IMO enough time to establish business as usual.
Once more:
I'm also looking for updates.
Is there any update on this?
Was the problem found?
Anybody has any news?

Charles copies me on the email correspondence, which basically consists of him getting more miffed by the day they haven't responded, and Korad coming up with a new excuse each time. I think the latest excuse is that they haven't finished the Labview driver!

I think both of us have given up all hope of ever getting the problem resolved. And Trio are left holding a bunch of these lemons in stock.

Dave.
 

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #145 on: October 29, 2012, 09:22:02 am »
And Trio are left holding a bunch of these lemons in stock.

Dave.
What Trio do have in stock, if your after a budget priced PSU, is the QJE PS-3005, it's no programmable, it's not the quietest electrically or audibly. Still at under $100, it remains a bargain and a good entry level alternative for those wishing for a basic 0-30V 5V supply.

http://www.triosmartcal.com.au/dc-bench-supplies/2631-qje-ps3005-bench-power-supply-150w-0-30v-0-5a.html

 

Offline ProBang

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #146 on: October 30, 2012, 10:15:32 am »

Hello

@ Dave

Very disappointing, how this manufacturer take care about his customers.  >:( :(

BTW:

I've seen the Korad PSU in the background during some videoblogs.
In the last blogs no more...
Find the PSU the way, following a ballistic curve, straight from the bench into the bin?

If not: Maybe you want to make some research to fix the thing?
(Of course: As far as it is possible for you.)
I think, it would be a great help for the owners of this unit.
Probably most of them are customers, who can't change to an agilent one.
Korad left them alone, as you can see...  :'(


@ Uncle Vernon

What a coincidence...
Possibly a bad man would say:" Two heads sharing together one mind - because it's more economic..."  ;D

I've bought exact this PSU some weeks ago. (The german re-badged version, you know.)

Look at this: http://www.electrobi.de/Energie/Netzgeraete-und-Netzteile/Labornetzgeraet-einstellbar/Labor-Netzgeraet-McPower-LBN-305-0-30V-0-5A-regelbar-LCD-Anzeige.html#review

It's far away from the league, where the Korad wants to play.
But it has one big advantage: It doesn't blow off my connected circuits.  :)

Greetings,


Hartmut
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Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #147 on: October 30, 2012, 12:17:49 pm »
I've seen the Korad PSU in the background during some videoblogs.
In the last blogs no more...
Find the PSU the way, following a ballistic curve, straight from the bench into the bin?
If not: Maybe you want to make some research to fix the thing?

I sent it back to Trio (it was a loaner after all).
I don't want anything more to do with it.

Dave.
 

Offline grenert

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #148 on: November 06, 2012, 01:47:49 am »
Charles copies me on the email correspondence, which basically consists of him getting more miffed by the day they haven't responded, and Korad coming up with a new excuse each time. I think the latest excuse is that they haven't finished the Labview driver!

I think both of us have given up all hope of ever getting the problem resolved. And Trio are left holding a bunch of these lemons in stock.
Couldn't see that one coming  ::)
There's a reason why One Hung Low companies all get lumped together as such.
 

Offline KORAD TECHNOLOGY

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #149 on: November 10, 2012, 06:44:41 pm »
Hello, for KA3005P, Charles has tested and all is excellent. And he will work with Dave to post the good video review very soon.  :)
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Offline David_AVD

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #150 on: November 10, 2012, 07:49:51 pm »
The plot thickens....   ???
 

Online PA0PBZ

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Keyboard error: Press F1 to continue.
 

Offline mikeselectricstuff

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #152 on: November 10, 2012, 09:27:38 pm »
Quote
Sticking "Lab Grade" on a product doesn't make it so."
Generally when you see things like "High Grade", "Professional" etc. actually written on a piece of kit it means the exact opposite.
Youtube channel:Taking wierd stuff apart. Very apart.
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Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #153 on: November 10, 2012, 09:32:31 pm »
... Dave to post the good video review very soon.  :)

Can't wait to see THE GOOD VIDEO. However, I have the feeling you will be a bit disappointed.
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Offline KORAD TECHNOLOGY

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #154 on: November 10, 2012, 09:53:15 pm »
... Dave to post the good video review very soon.  :)

Can't wait to see THE GOOD VIDEO. However, I have the feeling you will be a bit disappointed.

Thanks for your reply. I sincerely hope I won't  :)
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Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #155 on: November 10, 2012, 10:43:17 pm »
Oh, I think you will. Mwhahahahahahahahaha...



I'll go back to my cave.
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #156 on: November 11, 2012, 12:31:22 am »
... Dave to post the good video review very soon.  :)

Can't wait to see THE GOOD VIDEO. However, I have the feeling you will be a bit disappointed.

Thanks for your reply. I sincerely hope I won't  :)

It will depend entirely upon the performance of your product. Dave will give it a fair call, if the problem is gone and the fix looks permanent you may get something like the review you wish for.
 Ignore the talking heads in the cheap seats any review will be a fair call of the product as presented.
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #157 on: November 11, 2012, 02:47:19 am »
It will depend entirely upon the performance of your product. Dave will give it a fair call, if the problem is gone and the fix looks permanent you may get something like the review you wish for.
 Ignore the talking heads in the cheap seats any review will be a fair call of the product as presented.

Well, I have the feeling that Dave is not sufficiently motivated to do THE GOOD VIDEO. Asking him to remove the old video (or else?) probably didn't help to motivate him to do THE GOOD VIDEO.
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Offline grenert

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #158 on: November 11, 2012, 03:43:14 am »
Generally when you see things like "High Grade", "Professional" etc. actually written on a piece of kit it means the exact opposite.
"Quality Product"
 

Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #159 on: November 11, 2012, 03:59:11 am »
Clearly the original power supply transistors were completely insufficient for the task and blew up within a few minutes of use.

However, I fear that while Korad's modifications may pass the initial "Dave test" (i.e. the power supply works and performs well), they would be no good for long term reliability.

You cannot expect to make a decent linear power supply (30V, 5A) with a small heatsink and fan. Insufficient transistors will just make it fail quicker.

The only real world test I can think of is leaving it connected to a load at its maximum power dissipation (before a relay clicks in, and at the highst current possible), for several days, and see if it fails. That might give an idea of long-term reliability.
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #160 on: November 11, 2012, 05:19:18 am »
1V @ 5A ... That's torture
 

Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #161 on: November 11, 2012, 05:57:02 am »
Not necessarily, it has a relay clicking in at around 8V, so the worst case would be the greatest voltage drop across the power transistors at full load. Which may occur around 1V, or 9V, or 20V, depending on how it is designed.
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #162 on: November 11, 2012, 06:52:36 am »
how about 0.1V  ;D
39.5W is probably pushing the boundaries of what can be done with a aluminium sheet with holes punched in it to resemble a "heatsink" :-DD and slightly augmented with a fan that probably only achieves 20+ CFM and some pretty piss poor static pressure numbers.
I'm joking though but it can be true  :P It seems like this PSU really needs a LGA 775-ish heatsink (The OEM ones) as well as beefier transistors, not wimpy 2N3055s (Is it a 2N3055?) that only costs less than a dollar
Can't korad even fork out a few extra ten cents for a beefier transistor?  |O
« Last Edit: November 11, 2012, 06:54:24 am by T4P »
 

Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #163 on: November 11, 2012, 10:17:51 am »
This is what it takes to last 30 years. 35V, 3A supply using three Toshiba power transistors plus SCRs to automatically switch in transformer taps (three of them.) Plus an absolutely massive power transformer that's not going to saturate under load.

It cost me £30 from a local test equipment dealer, used of course - I'd hate to know what it cost new... It was made in Japan.
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #164 on: November 11, 2012, 11:20:47 am »
Well, I have the feeling
The feeling eh? Sure it's not a vibe? Feelings are the domain of soothsayers, charlatans, faith healers and other assorted crackpots.

Quote
Dave is not sufficiently motivated to do THE GOOD VIDEO
Given the interest shown in this particular supply, a follow up video would depend mainly on the availability of time and relevant and interesting content.

Quote
Asking him to remove the old video (or else?)
Or else? There you go having your feelings again. Dave has stated his position on such requests many times,  something that has nothing to do with your old country feelings or xenophobia

Quote
probably didn't help to motivate him to do THE GOOD VIDEO.
I am sure Dave will be overjoyed to think there are nutjobs out there that believe he'd put a desire for retribution before a need to call it as he sees it now. It may not be common practice amongst your secret handshake set but unless you've missed it completely, much of Dave's reputation is based upon his giving no bullshit calls based upon actual results.

I'll be interested to see what Korad has done to rectify problems and whether it constitutes a kludge to get it past testing or modification sufficient to give the thing adequate reliability and longevity.

Given that Dave will get an actual device and you're working from racial bias, tea leaves and other non specific jiggery pokery don't be offended if those of us with a clue wait for Dave's replies while ignoring your rants. Have a nice day!

 

Offline Ed.Kloonk

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #165 on: November 11, 2012, 11:23:23 am »
 :)
 
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Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #166 on: November 11, 2012, 01:36:28 pm »
My enthusiasm for a new video is almost zip.
But if people really want a follow-up, I might put it on the list.
Charles has a video of him using the new model for welding or something, as a hack test of it's gruntiness, he will drop it off in a few days and I'll probably put it on my Altzone channel.
No point doing another review as such, most of it was done in the previous video. So it would be looking at what they have changed and maybe some thermal and load tests etc.

Dave.
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #167 on: November 11, 2012, 01:51:38 pm »
So it would be looking at what they have changed

That would be the point of interest. Whether the degree of change warrants another video is your call.  Are these pieces of wonder a stock item at Trio again? I've seen no mention of them since removal?
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #168 on: November 11, 2012, 02:32:23 pm »
Are these pieces of wonder a stock item at Trio again? I've seen no mention of them since removal?

No, Charles is still waiting for replacement boards for the existing units he has in stock.

Dave.
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #169 on: November 11, 2012, 06:26:49 pm »
...

You know, in the US they sometimes say someone is two fries short of a happy meal. I think you are two test leads short of a multimeter. And two shrimp short of a barbie , if you get the drift.
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Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #170 on: November 11, 2012, 07:59:35 pm »
My enthusiasm for a new video is almost zip.
But if people really want a follow-up, I might put it on the list.
I'm interested, if we are to prioritize just behind the USB/portable/etc power supply progress report (assuming there is some progress).

Of course, all of them are coming behind the vids with Colin Mitchell and Doug Ford, but I assume those just one-off sort of things.
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #171 on: November 11, 2012, 08:21:31 pm »
You know
Maybe, but you're going to tell me right?

Quote
in the US they sometimes say ........
That is nice for them! In Borneo folks likely say something entirely different

Quote
I think you are
There is your mistake, you've kidded yourself that others, let alone my good self five a flying fourex what you think.  :-DD
Was it one of your flying generalisations like "all Asians are thieves" or some other manic rambling? You can answer if ou like just don't assume anyone is listening.  :D

We can reasonably conclude you have nothing of use or interest to offer on this topic.. 
 

Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #172 on: November 11, 2012, 09:36:11 pm »
Of course, all of them are coming behind the vids with Colin Mitchell and Doug Ford, but I assume those just one-off sort of things.

Colin was a one-off, he's in another state.
Doug will be back with a quite a few episodes.

Dave.
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #173 on: November 11, 2012, 10:08:31 pm »
...

Could you at least be a bit original and funny? I mean, just for once? Repeated racism accusations? How boring.
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Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #174 on: November 11, 2012, 10:21:24 pm »
Could you at least be a bit original
For you? Lemme see? Na, Nup, nada, not worth it!  ;)

Quote
and funny?
What you're not laughing? Must be taking yourself seriously again. That gives others a giggle and for that we thank you.  :-DD

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Repeated racism accusations?
must be in response to repeated racism. hmm?  ::)
 

Offline KORAD TECHNOLOGY

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #175 on: November 11, 2012, 10:43:32 pm »
... Dave to post the good video review very soon.  :)

Can't wait to see THE GOOD VIDEO. However, I have the feeling you will be a bit disappointed.

Thanks for your reply. I sincerely hope I won't  :)

It will depend entirely upon the performance of your product. Dave will give it a fair call, if the problem is gone and the fix looks permanent you may get something like the review you wish for.
 Ignore the talking heads in the cheap seats any review will be a fair call of the product as presented.

Hello, Uncle Vernon, thanks a lot for your support.   ^-^ I also believe Dave will give a fair call. Charles has made a good video and will post next week after he gets the repairing boards for his current 16PCS stock. Have a nice evening!
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Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #176 on: November 11, 2012, 10:55:00 pm »
...

No sorry kid, you lost your drive when you started to resort to spelling error correction postings to establish your superiority. And then you come up with racism accusations. Carefully chosen because it is nearly impossible to defend against such an accusation. By the way, did you clear that one with the leader of my fan club, Private Fluffer? He might be a bit upset if you didn't run it by him before posting.

By the way, have fun with a response. Guess what I'll do with it?
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Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #177 on: November 11, 2012, 11:01:18 pm »
Hello, Uncle Vernon, thanks a lot for your support.   ^-^ I also believe Dave will give a fair call. Charles has made a good video and will post next week after he gets the repairing boards for his current 16PCS stock. Have a nice evening!
I am not offering any particular support other than a sense of fair go, if the modifications to your supply are sufficient, I can see no reason why some of the initial enthusiasm for it cannot be revived.
I trust calls Dave or Charles will make and see it as ignorant that some will condemn on no basis other than country of origin. There is interest, by some,  in a follow up video, but as always it will be Dave's call what is produced and released.
 

Uncle Vernon

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #178 on: November 11, 2012, 11:11:37 pm »
No sorry kid
Haven't heard that one this century. Almost a compliment,  :)

Quote
to establish your superiority
It is heartening to see you have recognised this superiority, but there is no need for you to make any fuss, if you bow as I enter the room and covet your eyes, that will be entirely sufficient.

Quote
And then you come up with racism accusations.
A perfectly reasonable response towards repeated racism..

Quote
Carefully chosen because it is nearly impossible to defend against such an accusation.
It will be given your repeated racist remarks are embedded in all manner of caches and backups by now.

If someone who is simply bored at work and has nothing better to do than conjure up speculative crap about what the Chinese thought,

You work for Trio, don't you? But anyhow, feel free to kiss my arse any time it is convenient for you.

Oh, and I deal regularly with Chinese companies and engineers. Bunch of liars, all of them.

Quote
By the way, have fun with a response. Guess what I'll do with it?
If this is a lead-in to another of your rectal activities posts, then I'll choose not to guess thanks all the same.

Be nice to others.  ;)
« Last Edit: November 12, 2012, 01:27:37 pm by Uncle Vernon »
 

Offline LaurenceW

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #179 on: November 11, 2012, 11:34:54 pm »
I imagine that BAW's bed is up on six foot stilts, so that, whichever side he gets out of it, it's always the wrong side and leaves him fuming at the rest of humanity for the whole day, as a result.

I reckon
If you don't measure, you don't get.
 

Offline KORAD TECHNOLOGY

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #180 on: November 12, 2012, 12:56:22 am »
SO I'm confused.  Was Dave's unit a pre-production model that has since been fixed?  Or is there a flaw in all of the units on the market?

Call me crazy but I'm still considering buy one, if I can just confirm that the issue has been fixed or not.


Hi George, it is an early shipment(NOT a flaw) due to a few defective transistors. And now this issue has been fixed. The units  sent to our other representative are good and sell well. After Charles (Trio Smartcal) gets the boards to fix his current 16PCS stock, you can buy from him.  :)    Thanks for your support in advance!
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Offline Bloch

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #181 on: November 12, 2012, 07:58:33 am »

it is an early shipment(NOT a flaw) due to a few defective transistors. And now this issue has been fixed.
Is that the transistor on the back pcb ? Or are there more ?


After Charles (Trio Smartcal) gets the boards to fix his current 16PCS stock,
This is great! Can you upload here the old and the updated service manual (with schematic) ? So we can see that is updated ?
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #182 on: November 13, 2012, 05:29:49 pm »
Hi everyone, I received the modified power supply from Krissy at Korad just over a week ago.  So the first thing to do was to try and blow it up or burn it out to appease the trolls and for the interest of the more curious folks watching the thread.  In a nutshell I failed. The thing is still sitting beside me here with its output current-dependent fan going flat out.

What it was subjected to was:
- Set to 31.00V 5.100A and shorted the output. Left running for about 3 hours.
- Output shorted and the output switched on and off rapidly
- tried to use it as an arc-welder to stick the DMM probe to an alligator clip
- ran it at close to 150 Watts for about 5 hours
- rapidily switch the output on/off set to 31V 5.1A and a load connected
- ran it at 1V, 5.1A into a short circuit for 3 hours (this was more interesting from the current measuring DMM perspective...)

In summary, as we say here in Aussie-land the results were "as boring as bat-sh*t."  The thing is still working. I have never seen bat-sh*t, but I can endorse the validity of the adjective used in the comparison to a working power supply in steady-state conditions.

I did get that nice smell of warming plastic from the insulation on the alligator clips connected to the load. But nothing more spectacular than that.
I took a few thermal images of it too. Before I get trollisitc comments..  these were taken with the cover on because the cover forms part of the forced air cooling path. Highest temp I could see was about 77 degC on the transformer when it had been running at full load for over 2 hours. I'll upload those thermal images in the next post.
The one in this post is the power supply feeding the 10A input on a DMM.  It did this continuously for over 3 hours today and had no problems with being switched on and off rapidly.  You can see the area on the DMM where its fuse sits just behind the front panel. You'll see in the video, whenever I get it loaded, that this warming affects the DMM reading.  And before anyone comments, the DMM's had auto-powered-down and I'd got bored turning them on over and over again.


« Last Edit: November 13, 2012, 11:02:06 pm by TRIO_Smartcal »
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #183 on: November 13, 2012, 06:13:59 pm »
Here's some of the thermal images taken after the Korad KA3005P  had been running for a while.   

In the process I tried a couple of DMM's for the current measurement to see which warmed up the most and to see if it was possible to see where the internal shunt and fuse was without opening them. I'd got bored with the power supply at this stage. 

Anyway, I couldn't blow it up so when we get the parts to repair those we have in stock, they will go back on sale with a 2 year warranty.  If anyone wants to buy one, just mention EEVblog and we'll chuck-in at no charge a set of DMM test leads so you can use your old ones as welding rods....

http://triosmartcal.com.au/1713-tl-104-test-leads--alligator-clip-cat-iv-600v--cat-iii-1000v.html
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #184 on: November 13, 2012, 06:55:29 pm »
The warmed up DMM's are in the thermal pic's below.  These were an Agilent U1233A and an Agilent U1241A. I used a U1252A to keep an eye on the voltage.
During the soak-testing the current reading on the DMM's used to measure current steadily increased as they warmed up.
The power supply current reading did not change much at all. The voltage reading crept up marginally.
As most of you are probably aware, a DMM measures current by measuring the voltage over an internal shunt.
So what we were seeing with the slowly, but steadily, increasing reading on the DMM's was the internals of the DMM's getting warm, the internal resistance increasing with this temperature rise and the power supply giving a bit more voltage to keep the current at max.  The test leads will also play a part in this resistance path. We can see that the resistance of the leads and the DMM input is a combined 0.1 Ohms.

The normal picture below shows the DMM after it had been running for a while and the current reading had drifted up a bit. This was while we were testing at a setting of 1V, 5.1A.  The power supply went to constant current mode to deliver its max current and the compliance voltage necessary for this (0.5465V) is displayed on the U1252A.

It would have been more interesting if it hadn't all behaved as expected, but all ended up as hoped for.
We still have a working power supply and I got to play with a thermal camera.......
 ;D
« Last Edit: November 13, 2012, 07:15:10 pm by TRIO_Smartcal »
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Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #185 on: November 13, 2012, 08:15:17 pm »
Awesome follow-up, thanks Charles!

Dave.
 

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #186 on: November 14, 2012, 04:00:08 am »
Are you going to send a board to Dave to do his unit? Will be interesting to see the comparison and how it looks.
 

Offline Bloch

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #187 on: November 14, 2012, 04:03:36 am »
Are you going to send a board to Dave to do his unit? Will be interesting to see the comparison and how it looks.


Not possible - Dave send it to hell or there about[size=78%] [/size] :-DD
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #188 on: November 14, 2012, 08:43:38 am »
Dave sent the blown-up unit back here. Whenever we get the parts from Korad to fix it I'll take a few pics of any modifications and post them here.
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Offline EEVblog

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #189 on: November 14, 2012, 10:56:14 pm »
And here is Charles's video of of testing the new supply:


Looks pretty comprehensive, and if that abuse didn't kill it, I'm not sure what will.
Nice work Charles!

Dave.
 

Offline nitro2k01

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #190 on: November 14, 2012, 11:30:43 pm »
if that abuse didn't kill it, I'm not sure what will.
My own personal theory is that the error condition in the original test was produced by a race condition with the load. For example, the load is able to repeatedly overload and de-overload the supply very quickly such that the total current that passes through the supply through multiple pulses is enough to destroy something. Or, there's a comparator which triggers an interrupt on the microcontroller, which is triggered multiple times. This makes the microcontroller's interrupt stack to overflow, or something like that.

My point is, I would want the same scenario, with the electronic load, to be tested before giving the new unit the thumbs up.
Whoa! How the hell did Dave know that Bob is my uncle? Amazing!
 

Online SeanB

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #191 on: November 14, 2012, 11:43:57 pm »
Send it through the postal service wrapped in brown paper, that will destroy it.

Nice test, though I would like to see it being run until it does a thermal shutdown into a short circuit or into a 12V lamp in CC mode.

Is it me or does the micro stop scanning the display when changing voltage, leaving an arbitrary digit running at full power while doing so. It would be better for the firmware designer to blank the display when doing this, to keep from burning out the display digits.
 

Offline Stephen Hill

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #192 on: November 14, 2012, 11:59:11 pm »
Do you expect Porsche experience when you buy a KIA as well. Wouldn't be much sense in making Porsche's if that was the case.

KIA's come with a 7 year warranty...
 

Offline deephaven

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #193 on: November 15, 2012, 12:10:55 am »
One of the most important specs on a lab power supply for me is to never overshoot the set output voltage so as to avoid zapping the circuit it is powering. Would it be possible to do some of those tests with a scope attached?
 

Offline HackedFridgeMagnet

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #194 on: November 15, 2012, 12:30:19 am »
Quote
My own personal theory is that the error condition in the original test was produced by a race condition with the load. For example, the load is able to repeatedly overload and de-overload the supply very quickly such that the total current that passes through the supply through multiple pulses is enough to destroy something. Or, there's a comparator which triggers an interrupt on the microcontroller, which is triggered multiple times. This makes the microcontroller's interrupt stack to overflow, or something like that.
I agree with Nitro. I think.

When I saw the video of the fault occurring,  I had a thought along the same lines, ie. Constant watt load (if I remember rightly) and some sort of diverging control interaction going on between the two units.
Reproducing the circumstances of the failure so the new version could be tested under these circumstances would be a good validation of any fix.
If anyone could be bothered.
 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #195 on: November 15, 2012, 04:14:13 am »
A follow up would be nice.   8)

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #196 on: November 15, 2012, 10:03:35 am »
Do you expect Porsche experience when you buy a KIA as well. Wouldn't be much sense in making Porsche's if that was the case.

KIA's come with a 7 year warranty...

If you'd like me to raise the price to that of a Kia you can have a 99 year warranty   ;D
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #197 on: November 15, 2012, 03:59:08 pm »
Dave has posted a very amateurish video about our attempt to burn-out the Korad version 2.

It's a summary of the attempt. Obviously the video does not show the 12 or so hours we had it running for during the burn-out test.

Here's the link:  http://www.eevblog.com/2012/11/15/korad-psu-follow-up/

If you fall asleep during it that's OK, it's a power supply after all.  No car headlamp bulbs or items of test equipment were injured in the making of this video. We tried though.......
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Online BravoV

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #198 on: November 15, 2012, 04:24:09 pm »
What happened to other customers who bought this thing say from ebay type of deal ?  :-//

So practically they're screwed ?

 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #199 on: November 15, 2012, 04:42:26 pm »
How can we tell the difference? between the old model and the new "fixed" models? I'm in the US - and would prefer to buy from a US seller.

Offline pickle9000

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #200 on: November 15, 2012, 06:18:14 pm »

It's a summary of the attempt. Obviously the video does not show the 12 or so hours we had it running for during the burn-out test.


What kind of load for the burn in?
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #201 on: November 15, 2012, 06:25:02 pm »
A car headlamp. See here.....

http://www.eevblog.com/2012/11/15/korad-psu-follow-up/

Watch at 5 minutes in.
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #202 on: November 15, 2012, 06:52:00 pm »
What happened to other customers who bought this thing say from ebay type of deal ?  :-//

So practically they're screwed ?
I can only speak for Australia and NZ but all I can suggest is that you go back to where you bought it from if you have a problem. These things have different transformers for the supply voltage (as we are told)  so the 110V USA version might be OK.

We have had 2 failures here, one being the one we loaned to Dave and a unit we had sold. We contacted the people we had sold the others to and recalled them because the risk was too high with the nature of the fault if they blew up - pumping out 46V approx I seem to remember.  We offered customers another power supply on the link below as a no-charge replacement or they could wait for a fix.  They could get the same volts and amps from the replacement and they are linear too. No one was using it as a programmable anyway which made it easy.

http://triosmartcal.com.au/dc-bench-supplies/2432-atten-aps3003s-3d-dual-power-supply-0-30v-3a.html           

If there hasn't been a lot of reports from elsewhere about units blowing-up then it could be that we indeed got a dodgy batch and/or the Aussie mains supply voltage (typically around 240V-245V in the main metropolitan areas) was sufficient to let the smoke out of whatever they are using as a regulator.

It's interesting to see the amount of visibility this unheard-of low-cost power supply has received compared to some far more interesting products on the blog, but I think a lot of it stems from:
a) what it is specified to do for the price and
b) the intrigue generated about what was going to happen after it blew up. 

There's a post here that addresses the type of questions/comment like yours referring to "screwed."
There is a way to avoid being screwed by choosing not only on price. It's value and the elements that comprise it that matter.

http://www.eevblog.com/forum/blog-specific/eevblog-359-qdso-pocket-oscilloscope-review/45/

I suggest Krissy from Korad answers this next question.

How can we tell the difference? between the old model and the new "fixed" models? I'm in the US - and would prefer to buy from a US seller.
There is probably a range of serial numbers from this bad batch that should be known by Korad. I can't imagine there are only the 16 units we have here in the batch. So to use those timeless words... they are out there...  However I refer back to the supply voltage issue and if you are on mainland Europe you might just be OK. If you are in the UK you might have a potential issue.  The first units we received had 220V on the label on the rear. The one we can't blow-up has 240V on the label. That I suggest is significant. But Krissy @ Korad needs to answer this question and Krissy can also give you the name of their USA distributor if they have one.
« Last Edit: November 15, 2012, 08:05:44 pm by TRIO_Smartcal »
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #203 on: November 15, 2012, 11:00:31 pm »
Send it through the postal service wrapped in brown paper, that will destroy it.

Nice test, though I would like to see it being run until it does a thermal shutdown into a short circuit or into a 12V lamp in CC mode.

Is it me or does the micro stop scanning the display when changing voltage, leaving an arbitrary digit running at full power while doing so. It would be better for the firmware designer to blank the display when doing this, to keep from burning out the display digits.
Actually we ran it for a couple of hours with the filaments in parallel. The setting was max amps & max volts. It went into CC mode just the same as it did with output short circuit. Nothing happened. The compliance voltage was around 4.5V I think. The lamp just glowed as the filaments in parallel were sharing the 5.1 amps so their combined parallel resistance was still low hence the low voltage. Was so boring I didn't bother including it. I've got a bit of video though if anyone is desperate to see it. The big takeaway was just what a flexible load a head lamp bulb really makes :-)
« Last Edit: November 15, 2012, 11:28:27 pm by TRIO_Smartcal »
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #204 on: November 15, 2012, 11:20:04 pm »

I don't know what the margins at TRIOsmartcal are but the guy probably will have to sell a shit load of supplies to recoup the time he spent testing the supply.

Do you expect Porsche experience when you buy a KIA as well. Wouldn't be much sense in making Porsche's if that was the case.
Actually I didn't care about the cost of the time. Sometimes you put this sort of stuff before dollars per hour. I wanted to know as much as everyone else if it worked or not. If it was purely a commercial decision I would have scrapped the dodgy stock months ago and did something else. Given the effort put into this even if we fix them all we probably won't recover the full time and opportunity cost.  It`s also why I did a lot of it after beer-o-clock in the evening. If you closely look at the state of the alligator clip and DMM probe in the short circuit test you'll see that they are very burnt already. Before I took the video I knew this thing was OK. Hours spent for fun and interest and not gain. Hope that addresses your point.
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Offline JackOfVA

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #205 on: November 15, 2012, 11:28:53 pm »
For a quick and dirty intermittent short circuit test setup, use an old file and a nail. File to one side of the PSU, nail to the other and run the pointed end of the nail along the file.

Should see a bunch of sparks and a nasty looking current/voltage waveform.

Jack
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #206 on: November 16, 2012, 01:34:26 am »
We have a temp/humidity chamber in the cal-lab. I can assure you this is going nowhere near it.  We are not a company driven by bean-counters but I think we have done enough on this now.   
« Last Edit: November 16, 2012, 02:16:11 am by TRIO_Smartcal »
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Offline David_AVD

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #207 on: November 16, 2012, 07:39:47 am »
Let us know when they are back on the shelf and ready for sale.  I'm still interested in one (maybe two).
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #208 on: November 16, 2012, 08:09:17 am »
When we get the parts off Korad I'll put a post here. Hopefully it will not be too long.
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Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #209 on: November 27, 2012, 11:20:17 am »
Let us know when they are back on the shelf and ready for sale.  I'm still interested in one (maybe two).
Quick Update - The new output boards have been dispatched by Korad.  We are closely following the DHL shipment. As of posting they are in the air between HKG and SYD. We'll make another post here when they are back on sale after we have swapped the boards over and given the power supplies a bit of a work-out. We will have 16 units available then ex-stock Castle Hill (Sydney).
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Offline grenert

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #211 on: December 05, 2012, 11:11:54 am »
It looks like a little of Trio's QC costs are finding their way into the price  ;D
 

Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #212 on: December 05, 2012, 01:02:25 pm »
Also, there is no mention of the items being refurbished... I mean, they are better but the consumer doesn't know that from the product page.
 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #213 on: December 05, 2012, 01:24:53 pm »
Also, there is no mention of the items being refurbished... I mean, they are better but the consumer doesn't know that from the product page.

I wouldn't consider fixing a problem before sale "refurbished" - since these aren't returns - they are new. 

And I can't imagine anyone being upset that a flaw was fixed before it was shipped to them.  Unless you just like to complain about things.

Is there a person to contact at Korad to find out what range of serial numbers have this problem and how it effects the US market 110 volt models?  You know....for us in the states that want to pick one of these up?
« Last Edit: December 05, 2012, 03:45:08 pm by george graves »
 

Offline tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #214 on: December 05, 2012, 01:51:40 pm »
Eh, some people might care that they're not entirely original. Lawsuits have been made over less.
I don't care, just making a point.
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #215 on: December 14, 2012, 07:45:24 pm »
And they're back:
http://triosmartcal.com.au/2647-ka3005p-programmable-dc-power-supply.html
They're back and they are sold at $195+GST.  The web-guy didn't bring the price down when it was put back up there.

We've had one running for over a week now powering a car headlamp, both filaments in series at 30V across them. All was well. It got a bit warm and there was a strange glow from my garage.  Did it on a concrete garage floor just in case...   ;)

The other tests we did are here...   http://www.eevblog.com/2012/11/15/korad-psu-follow-up/

As for TOM66's comments, these are sold as new. If you were in the process of buying a car and  the dealer rectified a manufacturing defect before it was sold, it is not classed as used or refurbished. It is still new. This is no different. The warranty is as new.

Cheers folks!!
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Offline Scopeman1

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #216 on: December 15, 2012, 11:58:26 am »
Is there a person to contact at Korad to find out what range of serial numbers have this problem and how it effects the US market 110 volt models?  You know....for us in the states that want to pick one of these up?
A Korad person made some comments earlier. Perhaps if they are reading this they could give us the serial number range?
 

Offline Rick

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #217 on: January 01, 2013, 06:49:26 am »
By the way the ones sold on ebay are switchable between 110V and 220V.
I have also asked the question to SRA Soldering Products on Amazon.com, waiting for an answer.
On Amazon.com the prices are half the level in Australia and they ship by USPS priority mail.
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #218 on: January 01, 2013, 11:32:47 am »
Just be careful of the 220V instead of 240V transformer. I suspect there's little tolerance in the regulator design for handling much above the rated power.
Remember power is V^2/R and when you square 220V and 240V and compare, assuming a similar resistance, then power dissipation requirement goes up by 19%.  The ratio is the same on the LV side. 

Just food for thought but we know what happened to the 220V version we had. Given that in Metro areas of Australia the mains voltage is typically in the low 240's, personally I would not take the risk using a 220V version here in Aussieland.
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Offline Rick

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #219 on: January 01, 2013, 11:51:30 am »
Just be careful of the 220V instead of 240V transformer. I suspect there's little tolerance in the regulator design for handling much above the rated power.
Remember power is V^2/R and when you square 220V and 240V and compare, assuming a similar resistance, then power dissipation requirement goes up by 19%.  The ratio is the same on the LV side. 

Just food for thought but we know what happened to the 220V version we had. Given that in Metro areas of Australia the mains voltage is typically in the low 240's, personally I would not take the risk using a 220V version here in Aussieland.

Well I think the nominal mains voltage here in Turkey is 220V although I have seen variations between 215V and 235 V, but I think it is around 220V. I have just measured it right now with 3 different multimeters. It is 229V-231V...

My $70 power supply is meant to work with 220V+/-5% and this falls within these limits. No problem so far. What is the tolerance for KORAD as far as the mains voltage is concerned?
« Last Edit: January 01, 2013, 11:56:28 am by Rick »
 

Offline Rick

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #220 on: January 02, 2013, 02:55:52 pm »
By the way I watched the follow up video by Altzone. Is it better to use a 240V device if we live in an area where the mains voltage fluctuates between 215-240V? Actually it is mainly around 230V, I measured again.
 

Offline TRIO_Smartcal

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #221 on: January 02, 2013, 06:55:22 pm »
I don't think there is a simple answer to your question.

With these Korad's there seems to be two types of transformers. There is a 220V transformer that has a centre tap for 110V operation and a 240V transformer with no centre-tap so fixed 240V nominal operation.

From what I can see in the pictures that 110/220V  unit has definitely got the new version boards.  Plus it has a transformer labelled 220V.  Those are the same boards  as we received as replacements to upgrade our stock.  If there are two transformers needed (especially one for 240V operation), then that would indicate that the regulator board does not like too high a supply voltage.

The Korad's tolerance on mains-voltage does not seem to be specified on any documentation we have so it is difficult to to pass comment on your question. All I can do is reiterate that if something is designed for 220V and here in Australia it can go to 253V and still be in tolerance, then I personally would not take the risk.

Here's an interesting bit of reading. The  first paragraph 2.2.1 says it all........     http://users.metro2000.net/~purwinc/seec2_2.htm   .

The supply voltages were "harmonised" around many countries in the 220V-240V world, however all they did was really change the tolerance.   This allowed authorities to say 230V is the standard but power companies can continue using all their old 220V and 240V generation and distribution systems.  The way the voltages are now specified, means all will be still compliant but manufacturers have to build to that requirement if they wish to send the same products to multiple markets.  This does not seem to be the case with KORAD.

If you are in an old 220V country (now nominally 230V), and as you said Rick, your typical range is 215 to 235 then you haven't got a huge risk if you get the 110/220V version.....  HOWEVER..... and here's the crucial issue, Korad needs two transformers depending on the destination.  Why would they need to do this? Think about it because that's the $200 question....

So it's up to individual's choice to buy one with a 110/220V transformer and take the risk using it where the TYPICAL voltage is  >240V like in Australia and UK, (old 240V countries before "harmonisation").   All I can say is that if you are in an old 240V country and buy a 240V version then you also are probably OK.

The remaining question is "if you are in an old 220V country and you get a 240V version, (as you are suggesting Rick) will there be enough voltage from the mains supply, if it is at the low end of its tolerance (around 215V), to allow the power supply to deliver its full rated output voltage under full load....??"   

I suddenly feel a variac moment approaching......  but not now as "beer o'clock" is only 4 minutes away...


« Last Edit: January 02, 2013, 11:37:48 pm by TRIO_Smartcal »
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Online IanB

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #222 on: January 02, 2013, 08:44:07 pm »
One question for Korad is why not just build the thing with a 120/240 V transformer and avoid the need for two transformers? This ought to work fine as the USA and many parts of the world are nominally 120 V regions. If 240 V could over-volt a 220 V supply, then 120 V could similarly over-volt a 110 V supply.
I'm not an EE--what am I doing here?
 

Online BravoV

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #223 on: January 02, 2013, 09:00:04 pm »
One question for Korad is why not just build the thing with a 120/240 V transformer and avoid the need for two transformers? This ought to work fine as the USA and many parts of the world are nominally 120 V regions. If 240 V could over-volt a 220 V supply, then 120 V could similarly over-volt a 110 V supply.

Usually its just the matter of dumping the excess cheap stock (fixed volt version) from the transformer manufacturer or in their own warehouse, just don't expect components/parts consistency from this kind of company.
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #224 on: January 26, 2013, 07:05:21 pm »
I just bought a Korad 3005P supply, and following in my and Dave's footsteps, the first thing I did was take it apart!
I wanted to see if it was the new and improved version (the seller said it was... I need to make sure), and it is!
1) There is a 110/220v selector switch on the back.
2) The usb/serial board is the new one (choke on the board, NOT in the wiring from the transformer).
3) The output board is the green not the white material... (glass and not linen, cheap board).

Or course, I had to do MORE investigating.....
One thing I found that I did NOT like is the FWB was NOT bolted to the heatsink, but relied on the stiffness of the leads (they are very heavy) to hold it to the heatsink... BAD!!!!  so I pulled it apart, drilled a hole in the heatsink to pull it down to the aluminum, and did some minor bending to relieve some of the stress on the leads.
This, I thought, was pretty bad as the FWB is going to get hot.  It did have heatsink goop on it, but it wasn't flush!  I took pictures of this as well.

Then, I looked at the output transistors... they are 2sd1047... they are 120volt/12amp max, BUT ONLY 100watt max!  Seems a little close as far as dissipation.

There are two transistors and each one has a balancing resistor in it's collector so that they share the load.

There are two relays that switch the different secondaries... I measured (no load) the V+ bus and when the relays switch.
between 0 - 7v the bus is 17.4v
"  7.3 - 14.0  bus is 35.0
" 14.1 - 21.5 bus is 43.4  (sound familiar???)
" 21.5 - 31.0 bus is 58.5  (once again, sound familiar???)

The voltages between the four respective transformer leads are:
blk - white  32.5 vac
blk - red      43.5 vac
yellow - white 15.15 vac
yellow - red  26.3 vac
These are the combinations that the relays switch.
I didn't try the same test with a load, but I would imagine the relays may switch at different output voltages depending on load to keep the delta across the outputs within a range for regulation.

I also haven't looked at the turnon but that will be my next test.

The software is a little clunky but the ability to setup timed voltage stepping with different current limits is sort of nice for cycle testing... only thing is if the cycle is started and you stop it, you cannot restart it from time zero... it just continues from where you stopped it... NOT good!

Overall... for me, and the price and programmability, I am happy.... I have use HP supplies before (I used to work at Hughes Aircraft), and I do have a couple of Lambda bench supplies that are HEAVY and big, but this one will do what I want and hopefully won't fail like Dave's did.
 

Offline T4P

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #225 on: January 26, 2013, 09:12:36 pm »
Little close? Nah. If there are 3 taps it only needs to dissipate 50W, in any case any more than that results in requiring a MUCH larger heatsink anyway
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #226 on: January 27, 2013, 07:23:17 am »
Little close? Nah. If there are 3 taps it only needs to dissipate 50W, in any case any more than that results in requiring a MUCH larger heatsink anyway

Yes you are right... after I posted this I thought about what I said and realized that this is one of the reasons they have the four different bus voltage selections, to keep dissipation down, use small heatsink, "cheaper" transistors, smaller ballast resistors, etc.

One thing I am going to test is when the relays switch (changing voltage setpoint), does the output bounce around?  (this is a question that I am going to try and resolve).

Another thing... when switching the output on, is the relay switching causing the overshoot on turn on (another question I am going to try and answer)?

This would indicate to me that the output should be enabled FIRST, then applied to the binding posts after a short delay (after the supply has settled), and I might just makeup a delay to do this so I don't cook something from the turn on overshoot.
 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #227 on: April 24, 2013, 10:15:55 am »
For USA folks.  SRA solder has these on sale for $95 shipped on ebay today.

http://www.ebay.com/itm/KORAD-PROGRAMMABLE-PRECISION-VARIABLE-30V-5A-DC-POWER-SUPPLY-DIGITAL-LAB-GRADE-/110888868115?pt=LH_DefaultDomain_0&hash=item19d17dd913

The ebay user id is randyruby - but it's SRA solder.

I couldn't resist - I order two.

Offline hgg

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #228 on: May 14, 2013, 06:27:01 pm »
Hi,

I would like to buy a bench power supply and I think I will buy the programmable Korad.
http://www.ebay.com/itm/110888868115

Apart from the stability problems that they are supposed to be fixed, I've seen some cases
were the main power on/off switch has failed.  Do you know if they have fixed that as well?

Some questions for the owners of this power supply:
- Is it silent?  Is the fan always on, or only when needed?
- Does it make any hissing noises with a load or without one?
- Does it have any overshoot problems?

I am already over-budget by buying this power supply.  Do you think its a good option for
the money?  Are there any better ones for a similar price?  (not used ones)

Thank you!
 

Offline iloveelectronics

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #229 on: May 14, 2013, 06:44:00 pm »
I would like to buy a bench power supply and I think I will buy the programmable Korad.

Try the Vantek 3305P instead. There was a thread on this PSU some time ago: http://www.eevblog.com/forum/reviews/vantek-dps-3305p-32v5a160w-programmable-dc-power-supply/

It doesn't overshoot, and it actually has 5 preset buttons for M1 to M5 :D, and they work as they are supposed to. I read before that the Korad's presets don't really work the way they should, you could change the settings even without overwriting them explicitly.
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Offline hgg

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #230 on: May 14, 2013, 07:17:21 pm »
...but do you know where can I buy the Vantek from?
(I live in Greece).
 

Offline iloveelectronics

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #231 on: May 14, 2013, 08:03:28 pm »
...but do you know where can I buy the Vantek from?
(I live in Greece).

Here's one on eBay: http://www.ebay.com/itm/Programmable-Variable-Adjustable-DC-Power-Supply-0-32V-0-5A-USB-AC-110-220V-/281101170639?pt=LH_DefaultDomain_0&hash=item4172ef77cf

But make sure you confirm with the seller you're getting the Vantek or Caltek branded ones. Apparently identical looking units with a different brand name do overshoot.

I have also sourced a couple of these for another forum member some time ago. The one I bought for my own use very recently seems to look different internally though, perhaps they have revised the design since that discussion thread above in 2011.
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Offline hgg

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #232 on: May 14, 2013, 09:09:33 pm »
Hi, thanks I will check that out, although it ships from China...

So do you mean that the Konrad is a re-branded Vantek ???
 

Offline hgg

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #233 on: May 14, 2013, 09:36:26 pm »
I also saw in the photos that the Vantek has a toroidal transformer.
I assume that this is better, correct?
 

Offline iloveelectronics

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #234 on: May 14, 2013, 11:22:28 pm »
Hi, thanks I will check that out, although it ships from China...

So do you mean that the Konrad is a re-branded Vantek ???

As far as I know, no, they are manufactured by different companies.
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Offline iloveelectronics

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #235 on: May 14, 2013, 11:41:20 pm »
I also saw in the photos that the Vantek has a toroidal transformer.
I assume that this is better, correct?

I think there are pros and cons, but I'll leave this to the more qualified and knowledgeable members to answer.
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Offline hgg

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #236 on: May 15, 2013, 05:08:24 am »
In the case of the Korad, I can only find the one with the 220V transformer.
I've heard that there is a version with a 240V transformer as well. 
Here in Greece we have 230V.  Do you think I will have any problems?

Thanks.
 

Offline madires

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #237 on: May 17, 2013, 06:16:54 am »
In the case of the Korad, I can only find the one with the 220V transformer.
I've heard that there is a version with a 240V transformer as well. 
Here in Greece we have 230V.  Do you think I will have any problems?

Should work fine since a proper PSU is designed to run with 10% under/overvoltage.
 

Offline hgg

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #238 on: May 17, 2013, 07:53:14 am »
Just bought it.... Thanks.   :)
 

Offline nelsonro

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #239 on: May 25, 2013, 12:24:50 am »
Found a different kind of fail with a re-branded tenma psu... if you look at the model it says 2x 3A outputs + 1 fixed 5v rail but this unit its a 2x 5A output with no extra 5v rail lets just hope they didin't just flash the wrong firmware in it  |O to make it go to 5a.
http://imgur.com/klQRcZm

didn't notice at the time but this one doesn't have pc connection.
Also tldr all so don't know if anyone found how to go to m5... actually found it by accident, just press m4 and rotate the adjust knob clockwise
 

Offline leniwiec

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #240 on: January 07, 2014, 09:52:49 am »
I also have two of them, and now warranty for them had ended, so I decide to make it less noisy ;-) If somebody interest, take a look on my ultra simple hack here http://www.leniwiec.org/en/2014/01/06/korad-ka3005d-silent-fan-hack/

Cheers!
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #241 on: January 07, 2014, 12:48:13 pm »
Took a look at your mod (not really a hack though) and left you a comment.  Nice work and I just might do the same.
My supply may be a later one though as on the heatsink, every other finger is bent over so the air must pass by the fingers.
I have had the thermal trip the supply due to overheat, so a larger heatsink seems to be the way to go!
 

Offline leniwiec

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #242 on: January 07, 2014, 02:52:26 pm »
Thx pomonabill221. Yes, it is nothing big, I just wrote about it because want to share my opinion about this units ;)
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #243 on: January 07, 2014, 02:57:27 pm »
Thanks!
Thx pomonabill221. Yes, it is nothing big, I just wrote about it because want to share my opinion about this units ;)
Thanks!  Yes it is a cheapy and has "limited" performance, but it isn't an HP/Agilent/Lambda and it doesn't have the price tag either!  Just remember that when using it (really a comment to everyone).
 

Offline GiskardReventlov

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #244 on: February 01, 2014, 09:55:50 am »
A general question about the testing process.  I've seen this in other videos here too. Dave had his BK connected to the Korad. No doubt I'm missing some basic knowledge here. Why did he have power going in to a power supply? I know he touched on this but I didn't get it. It seems this was important to revealing the failure, right?
 

Online jancumps

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #245 on: February 01, 2014, 10:04:23 am »
A general question about the testing process.  I've seen this in other videos here too. Dave had his BK connected to the Korad. No doubt I'm missing some basic knowledge here. Why did he have power going in to a power supply? I know he touched on this but I didn't get it. It seems this was important to revealing the failure, right?
That device can sink power. He uses it as a configurable load.
 

Offline GiskardReventlov

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #246 on: February 01, 2014, 10:12:39 am »
That device can sink power. He uses it as a configurable load.

"That device" == "He uses it" == BK?

If my understanding's correct above, you're saying that the BK can handle power in either direction. Is that right. It can act as a multimeter. I think he said that in the video but I wasn't clear on that.  I think he did same in the Rigol DP832 video (which also had serious issues).

If my understanding's not correct of what you meant, then what did you mean?
 

Online jancumps

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #247 on: February 01, 2014, 10:17:13 am »
That device can sink power. He uses it as a configurable load.

"That device" == "He uses it" == BK?

If my understanding's correct above, you're saying that the BK can handle power in either direction. Is that right. It can act as a multimeter. I think he said that in the video but I wasn't clear on that.  I think he did same in the Rigol DP832 video (which also had serious issues).

If my understanding's not correct of what you meant, then what did you mean?

It is a programmable load. So you can configure the amount of load it will apply to the source.
" A configurable consumer of energy "
 

Offline GiskardReventlov

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #248 on: February 01, 2014, 10:29:54 am »
It is a programmable load. So you can configure the amount of load it will apply to the source.
" A configurable consumer of energy "

That makes a lot of sense, thanks!

I would never spend money on this Korad.  Dave is a good man, because this thing is a disaster and I believe he was being quite generous to Charles and Korad. Maybe Korad shoud be looking for new hires. There are literally millions and millions of college graduates in China looking for work.

Now I will go look to see if he reviewed any legacy PS that can be found for low $, these new low $ supplies are too much crap. Buying one at any price encourages them to keep making them. Dave's become their personal Quality Control engineer.
 

Online jancumps

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #249 on: February 01, 2014, 10:56:13 am »
It depends on what you need. My PS is crappier than that Konrad and it serves me well.
As long as you know the limits, and the limits don't stop you from doing your work...
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #250 on: February 01, 2014, 11:00:44 am »
The version of the Korad that Dave destroyed is an old one and Korad has upgraded the supply (the output transistors).
You really need to do a little more research on the supply before you completely write it off and call it crap.
Yes it is a cheap supply, but for what it does, and for what it costs, it is ok for most.

I have two Lambda supplies (an LQ-531 ( 20v/8.6amp and LQ=533 60v/3.3amp) and they are tons better than the Korad, BUT are about 3x heavier and at least 2x larger.  For my testing, I use the Korad and knowing the limitations and faults, the Korad is just fine.

If you want to be a brand snob... so be it, so good luck finding a "good" supply for around 100 that is remotely programmable.

Did you even bother to look at the schematic and understand what is going on?  May be educational as well.

Seems strange that you are bashing the Korad but you didn't even know that the B&K was a programmable dummy load!
« Last Edit: February 01, 2014, 11:02:58 am by pomonabill221 »
 

Offline GiskardReventlov

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #251 on: February 01, 2014, 12:21:34 pm »
If you want to be a brand snob... so be it, so good luck finding a "good" supply for around 100 that is remotely programmable.

First I think you should refrain from name calling it makes you look bad and it makes it look like you want to avoid discussing the reality.
You're throwing brand names around and you seem to be personally offended by completely deserved criticism. Do you have a stake in Korad?
As for wishing luck, I wouldn't pay $5 for that, it's a waste of my time.  You need to understand that crap is crap no matter what the price.

And I never saw him do any remote programming with it, we don't know if it works.

Quote
Seems strange that you are bashing the Korad but you didn't even know that the B&K was a programmable dummy load!

Again trying to deflect the real issue.  Explain how or why that's relevant to discernment of that Korad crap.
And that issue is that people should either find a good used supply for similar price point or save up some more and get good quality that's reliable, that has sound and logical thought behind it and that's safe to use with confidence.

I watched the teardown, like I said Dave was really generous.

Here's a previous quote which sums it up well:

I wasn't impressed with the teardown stage. Everything is 'there' to get a DC programmable PSU, but it seems rubbish built. Uncleaned PCB's, random holes drilled, poor soldering, weird R2R DAC (apparently PCB space and SMT parts placing is free for them) and overall shitty stuff :)

Well said Hans.
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #252 on: February 01, 2014, 12:33:58 pm »
You have your opinion... we all have ours...
Whatever blows your skirt up!
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #253 on: February 01, 2014, 06:13:20 pm »
@GiskardReventlov

You are running in the classic problem here. Those who bought it will defend their buying decision with teeth and claws. AKA choice-supportive bias http://en.wikipedia.org/wiki/Choice-supportive_bias You have the same here with people defending their shitty multimeters.

The Korad is the Yugo of programmable power supplies. Let them drive around in their Yugos and pretend they are driving Porsche, making some va-va voom voom sound with their lips.
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Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #254 on: February 01, 2014, 06:35:10 pm »
I never said it was a porch (that is what I think of overpriced VW's).
I know it is a cheapy, and not having a job right now, I have to watch what I spend.
If you would like to give me a high priced power supply, do so... I won't refuse a freebie.
I am NOT defending the supply... I know it has alot of problems/limitations, but for what I use it for, it fits my purpose.
I could drag out my Lambda's, but they are big, take up a lot of room, and I don't need that precision for what I am doing right now.
I don't know why I even responded... the complainers here are obviously just complaining about nothing... what do they have that is better?
 

Offline GiskardReventlov

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #255 on: February 04, 2014, 10:02:18 am »
AKA choice-supportive bias

I know, sometimes it's so bad though that I can't refrain.  But mostly people have to realize it ain't personal. In fact it's painful to see and in some cases (e.g. PS and multimeters) there are real and significant safety issues.

If calling out a heap-O-crap was just complaining Korad would never have fixed it.

But it's also very entertaining to see what horrors Dave reveals. So for that we are grateful.
 

Offline jonathanpatate

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #256 on: February 05, 2014, 06:58:08 am »
Hello from France. Here this PSU can be bought under the Velleman brand with the PS3005D reference.
As said before, it seems to be an upgraded version, so it bought one, and yes it is !

The fan is noisy and the buzzer stay weird too.

But the encoder for selecting voltage or current is now "stem" (with steps).
The 7-segment displays are well aligned/positioned (no more gap between the decoration window).
Some caps are Rubycon, others stays cheapo.

See pictures.
« Last Edit: February 05, 2014, 07:03:21 am by jonathanpatate »
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #257 on: February 05, 2014, 07:03:44 am »
That's a spittin' image of my Korad!  Not surprising though EXCEPT your front panel shows a M5 where mine shows LOCK (panel lock).
 

Offline jaxbird

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #258 on: February 06, 2014, 01:53:21 am »
@GiskardReventlov

You are running in the classic problem here. Those who bought it will defend their buying decision with teeth and claws. AKA choice-supportive bias http://en.wikipedia.org/wiki/Choice-supportive_bias You have the same here with people defending their shitty multimeters.

...

It works both ways.

Frequently even stronger for those who spent a larger sum on a brand name, refusing to acknowledge that a cheaper product, can be adequate, perhaps even superior in some areas, and capable of performing the same duty.

One thing I do find interesting, are those, having no personal experience with a specific product, feeling the need to express strong (often 2nd hand) opinions about it's qualities.

Analog Discovery Projects: http://www.thestuffmade.com
Youtube random project videos: http://www.youtube.com/user/TheStuffMade
 

Offline David_AVD

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #259 on: February 06, 2014, 07:55:29 am »
I bought one of those Korad units.  It feels somewhat nasty to use (poor action of the buttons mainly) but I guess I got what I paid for (just).  I don't think I'd buy another one though.
 

Offline Electro Fan

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #260 on: February 09, 2014, 11:15:37 am »
Everyone has their opinion but for what it's worth the KA3005P I've been using has been solid.  It's easy to operate (the buttons, display, and dial work fine) and it checks out reasonably close to my DMMs (including a Fluke) and voltagestandard.com devices.  For the price it's a good value.

Here are some reviews from other users:
http://www.amazon.com/KORAD-KA3005P-Programmable-Precision-Adjustable/product-reviews/B0085QLNFM/ref=cm_cr_pr_top_recent?ie=UTF8&showViewpoints=0&sortBy=bySubmissionDateDescending
 

Offline 3w_049

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #261 on: March 09, 2014, 03:00:29 pm »
For USA folks.  SRA solder has these on sale for $95 shipped on ebay today.

http://www.ebay.com/itm/KORAD-PROGRAMMABLE-PRECISION-VARIABLE-30V-5A-DC-POWER-SUPPLY-DIGITAL-LAB-GRADE-/110888868115?pt=LH_DefaultDomain_0&hash=item19d17dd913

The ebay user id is randyruby - but it's SRA solder.

I couldn't resist - I order two.

The price has gone up significantly, hurry before it costs more than Agilent craps.
 

Offline madires

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #262 on: March 10, 2014, 02:14:49 am »
Just saw the Korad at a local online shop, EUR 80 for the KA3005D and EUR 100 for the KA3005P (RS232 & USB).
 

Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #263 on: March 10, 2014, 08:22:35 pm »
Can somebody outline the programming capabilities over USB/serial? I assume you can control it from PC but can you also read the values on display? Can you also log them? Any programming capabilities/API/command line/etc?
 

Offline poorchava

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #264 on: March 11, 2014, 01:31:44 am »
IMO programming PSU from PC is useful if you are trying to do some automated testing or stuff. I've built myself a PSU that can be connected to the PC and I find it that it's easier to just turn the knob or press 'recall from memory'. That's it.
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Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #265 on: March 11, 2014, 05:14:04 pm »
Obviously dialing 5V for example is easier without going through the computer but I'm interested to either program it to use some specific algorithm or to log how much energy goes to something or how long it takes.

I looked at some screen shots and for now it looks it has the capability to set whatever (or most of what) the front panel buttons set and also some time-based "scripting"/change of some parameters.

However, I don't know for now:

- if it reads at all to the computer the actual values
- if you can do anything with them (like vary the voltage depending on the current, or maybe even current and time, etc)
- if there are some scripting capabilities so you can read/write whatever you want to the PS.

Other than that what would be a simple way to tell if you're getting the "good" version? I assume the decent shops by now should have the good one anyway but checking would be good.
 

Offline Bored@Work

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #266 on: March 11, 2014, 05:40:22 pm »
Obviously dialing 5V for example is easier without going through the computer but I'm interested to either program it to use some specific algorithm or to log how much energy goes to something or how long it takes.

I looked at some screen shots and for now it looks it has the capability to set whatever (or most of what) the front panel buttons set and also some time-based "scripting"/change of some parameters.

You will find one of the problems these things have is you can't precision-time the settings. That is because of the programming interface, but also because of the PSU. Especially reducing the output voltage is a problem, because these things have caps at the output and their discharge rate depends on the load. The lighter the load, the slower the voltage change. What they don't have is what is called active down programming, an instrument-controlled rapid discharge path over the output cap(s).

You also can not precision-time the readings. I.e. if you think of a sampling system, you have one with a lot of jitter in the sampling frequency. And this becomes even more apparent if you want to calculate things like power. This requires two separate readings I and V, which should be from the same time but are not. And each reading itself has a jitter with respect to the sampling frequency. The result is you can only measure very slow changing DUTs.
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Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #267 on: March 11, 2014, 07:19:48 pm »
That's correct indeed, if there's any significant variation (even for what is considered low frequency, like 10Hz) the measurements might mean nothing and/or the CV (and even CC) might not answer fast enough.

Speaking of that I think it would be worth having some tests and explanations from Dave on the pitfalls of power measurement when you can's assume the waveform and the phase of the voltage/current. Let me try to find if there's some thread with ideas for future videos :-)

In any case for this application I don't care much of "fast change" is just some kind of glorified charger/test bank.

 

Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #268 on: March 14, 2014, 09:59:04 pm »
Ok, I think I can answer the questions myself: as somehow expected the protocol is easy enough and reasonably complete (I assume is the same as for the Velleman clone): http://sigrok.org/wiki/Velleman_PS3005D/Info

This starts to go from "fail" to "best buy" in the "cheap" sector, at least in Europe where the cheapest 30V 5A seems to be about 70eur. And of course is not programmable, just one of the basic fine/coarse volts/amps, with only 3 digits on both A and V, without memories, without the possibility to set the current/disconnect load/etc. And of course you REALLY don't know what you get inside the box and for sure they try to skimp as well on power/expensive components.
 

Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #269 on: March 16, 2014, 10:03:05 pm »
I've got one for myself for 99 eur from reichelt.de.
Not much to complain yet, except that the binding posts are now "internal" (multimeter-like) connectors. Of course, that makes them better safety-wise (they too take shrouded banana plugs) but still a bit of a bummer. Any (ebay?) recommendation for some cheap banana->binding post adapters that can take a couple amps?
 

Offline soren

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #270 on: December 05, 2014, 09:28:18 am »
Reichelt had the KA3005D on sale for 55 EUR last Friday, so I bought one.

I was a little concerned to see that it has the silly old M5 memory slot instead of a LOCK indicator, but despite this it seems to be a recent build.

Some impressions:

The power transistors are a pair of Toshiba 2SC5198's, which should be easily up to the task. I wonder what type the old ones were.

The fan sounds like it is decent quality but it's quite loud because of chassis turbulence and being run unnecessarily fast. Maybe I'll just add a series resistor as the exiting air isn't too warm even when the power supply is at maximum thermal load.

General soldering quality is good, but the hand-inserted components are all just thrown in rather carelessly. In my case, the overload thermistor had its leads shorted and it also wasn't really pressed up against the heat sink.

The three large caps marked Rubycon may look okay in the picture, but they feel very rough to the touch and unlike real Rubycons, so I suspect that they are instead "con rubies".

The 7812 on the controller board has a tall heat sink that is only attached to the regulator and doesn't even rest against the PCB. Extremely wobbly to the point where I'm a bit surprised that it didn't break off during transport.

No overshoot! Discharging the output cap takes half a second with no load.

Calibration is easy and works fairly well. There's some drift, but that's okay. I didn't expect this to be a precision product.

Pressing the mechanical power switch to turn the power supply on causes a fairly strong burst of noise which doesn't appear if the switch is left on and the IEC cable inserted instead. Having read about previous runs of this PSU in the 120V version, which had lots of problems with the power switch, I wonder if they are still using that same weak switch in the 230V product and if it might be underspecified even there, causing arcing. It's also only a single pole switch.
 

Online Andreas

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #271 on: December 06, 2014, 10:09:44 am »
Hello soren,

Thanks for the teardown and the measurements.
I also couldnt resist on black friday for 55 EUR.
And some weeks ago the KA3005P went for 79 EUR as a computer controlled powerstage for my peltiers.

I do not think that the fan is unnecessarily fast.
In some special situations driving into 5A current limit from high voltage repeatedly
 (so that the relay switches happily) you are using up the SOA of the transistor at 25 degrees.
If you have higher temperatures you will be above SOA.

So I think I will order some 2SC5198 just in case....

With best regards

Andreas
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #272 on: December 06, 2014, 10:47:12 am »
Has anyone been able to run the software for the KA3005P on windows 7 64 bit?
If so, what was the software and version?
I have not had any luck with mine... did work on win2000, but 7 is a no go.
 

Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #273 on: December 06, 2014, 08:55:59 pm »
Yes [it runs on win7-64], I'll let you know when I have access to that box, can't remember if it was Korad or Atten software.
Can't remember if it was over serial or over usb/virtual port - most likely usb.
BTW does the PS come with a serial cable? I can't remember and if it does I can't remember where I put it (if I ever had it) and is nagging me. Not that I don't have plenty of serial cables...
 

Online Andreas

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #274 on: December 06, 2014, 09:30:53 pm »
Hello,

I have tried the software on a Win XP system. (of course with blocked internet access).
The function of the software was fine but
the XP system had unusual (unstable) behavior after installation.
So I uninstalled the software. And system behaved as before.

For me the software seems to be somewhat crappy or even dangerous.
There is one file left after deinstallation. (KA3005P.aliases)

content:
[ÎҵĵçÄÔ]
ÎҵĵçÄÔ = "localhost"

That what I do not understand:
so for what in the world does a simple control program
for a power supply need a network access?

With best regards

Andreas

edit:
BTW does the PS come with a serial cable?
Mine came only with the (light blue) usb cable for connections.


« Last Edit: December 06, 2014, 09:33:18 pm by Andreas »
 

Offline george graves

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #275 on: December 06, 2014, 09:33:06 pm »
Win 7 pro - no issues here.  Sorry, don't have the version number since I re-installed windows.  I think I downloaded it from their site.

The power supply has been running great - bought two - no issues.


Offline rr100

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #276 on: December 07, 2014, 01:09:49 am »
Ok, my (as in the one I've found first...) software is called "KA3005P PROGRAMMABLE DC POWER SUPPLY V2.4". I really can't remember where I have it from but it was for sure linked from one of the big(ish) suppliers like digikey or something similar (somebody somehow trusted, at least in my mind...). It works on win7-64 but I did not test it for long time, the program looks fine but I wrote mine (see the quote below).
If the original software is so fragile like my software as at first for sure it won't be very reliable to be run for longer time (there's some garbage coming now and then).

Even if it is python and console-only mine won't work on windows without some rework, it is a tricky task (and os-dependent) to just read keys from the keyboard.

Well, I guess I can at least share what I've done until now.

https://github.com/vb0/korad/

From README

=========================
THIS IS HIGHLY EXPERIMENTAL
USE AT YOUR OWN RISK
WORK IN PROGRESS
This will control a KA3005P lab power supply
The device is hard coded (this is my default usb->serial device on raspi): /dev/ttyACM0
I've used quite a few modules (maybe too many), the only one a bit off-the-beaten-track should be https://github.com/magmax/python-readchar
Usage:
run kcontrol.py
It will output every 1.x seconds or so (there are some "hard" coded timers that can be easily changed) something like:
44mA 5.00V 0.22000W 0.25496mWh 0.050993mAh 4.3s SET:700mA 5.00V
As the power supply is locked for many seconds after any serial command I have added the following rudimentary controls:
v V lower v is voltage "-0.01", V, as in shift+v is +"0.01"
i I current down and up
o O output off/on
q quit
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #277 on: December 07, 2014, 06:12:52 am »
Yes [it runs on win7-64], I'll let you know when I have access to that box, can't remember if it was Korad or Atten software.
Can't remember if it was over serial or over usb/virtual port - most likely usb.
BTW does the PS come with a serial cable? I can't remember and if it does I can't remember where I put it (if I ever had it) and is nagging me. Not that I don't have plenty of serial cables...
Thank you for the reply!
My PS did not come with a serial, only a USB cable, but I prefer USB anyhow, so don't be nagged any more!  :-DD

Thanks for the info though! I will look further and try and find the SW... I could use it for a few simple things...
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #278 on: December 07, 2014, 06:26:51 am »
Hello,

I have tried the software on a Win XP system. (of course with blocked internet access).
The function of the software was fine but
the XP system had unusual (unstable) behavior after installation.
So I uninstalled the software. And system behaved as before.

For me the software seems to be somewhat crappy or even dangerous.
There is one file left after deinstallation. (KA3005P.aliases)

content:
[ÎҵĵçÄÔ]
ÎҵĵçÄÔ = "localhost"

That what I do not understand:
so for what in the world does a simple control program
for a power supply need a network access?

With best regards

Andreas

edit:
BTW does the PS come with a serial cable?
Mine came only with the (light blue) usb cable for connections.

Interesting that the OS was affected!  I, too, would remove the software if it affected my OS!  Don't need any more problems.
Strange file left behind?!?!?!  I agree... why do they need internet access  unless there was something in the help file, or "software upgrade"?

Thanks for the info!
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #279 on: December 07, 2014, 06:31:06 am »
Win 7 pro - no issues here.  Sorry, don't have the version number since I re-installed windows.  I think I downloaded it from their site.

The power supply has been running great - bought two - no issues.
hhmmm.... I'll take a look and try it again.

I really only need it for a simple cycling test I want to run.. no real precision (I'm using my meters for that).
Mine has been running just fine as well for at least a year also.

Charging batteries, testing leds, supplying power for various testing, etc.

  Just remember the power turn on bump!  Mine has that, but others report theirs do not....
Overall, I do like the supply... it's small, fairly lightweight, and for what I want works fine.
 

Offline pomonabill221

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #280 on: December 07, 2014, 06:35:09 am »
Ok, my (as in the one I've found first...) software is called "KA3005P PROGRAMMABLE DC POWER SUPPLY V2.4". I really can't remember where I have it from but it was for sure linked from one of the big(ish) suppliers like digikey or something similar (somebody somehow trusted, at least in my mind...). It wor