Author Topic: EEVblog #315 - Korad KA3005P Review/FAIL  (Read 166631 times)

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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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Uncle Vernon

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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.

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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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Online 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.
 

Online 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 »
 


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