Author Topic: EEVblog #315 - Korad KA3005P Review/FAIL  (Read 251862 times)

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Offline pickle9000

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #200 on: November 15, 2012, 07:18:14 am »

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, 07:25:02 am »
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, 07:52:00 am »
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.

https://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, 09:05:44 am 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, 12:00:31 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, 12:28:27 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, 12:20:04 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, 12:28:53 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 15, 2012, 02:34:26 pm »
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 15, 2012, 03:16:11 pm 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 15, 2012, 08:39:47 pm »
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 15, 2012, 09:09:17 pm »
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, 12:20:17 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 johnboxall

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Offline grenert

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #211 on: December 05, 2012, 12:11:54 am »
It looks like a little of Trio's QC costs are finding their way into the price  ;D
 

Online tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #212 on: December 05, 2012, 02:02:25 am »
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, 02:24:53 am »
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, 04:45:08 am by george graves »
 

Online tom66

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #214 on: December 05, 2012, 02:51:40 am »
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, 08:45:24 am »
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, 12:58:26 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: December 31, 2012, 07:49:26 pm »
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, 12:32:47 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, 12:51:30 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, 12:56:28 am by Rick »
 

Offline Rick

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #220 on: January 02, 2013, 03:55:52 am »
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, 07:55:22 am »
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, 12:37:48 pm by TRIO_Smartcal »
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Offline IanB

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #222 on: January 02, 2013, 09:44:07 am »
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.
 

Online BravoV

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Re: EEVblog #315 - Korad KA3005P Review/FAIL
« Reply #223 on: January 02, 2013, 10:00:04 am »
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, 08:05:21 am »
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.
 


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