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Author Topic: EEVblog #315 - Korad KA3005P Review/FAIL  (Read 138355 times)

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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
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Offline [email protected]

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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Firstly yes we have withdrawn this from sale until we get to the bottom of the failure.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  [email protected] 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
 

Uncle Vernon

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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 »
 

Online 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 »
 

Offline 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!  ;)
 

Offline 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.
 

Offline EEVblog

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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.

Dave.
 

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.
And the Fluke EMC issue
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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
(PS: Full power is actually 4.5Amps per channel at 30V ... )
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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
 


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