A batch of STK795-821 with a bizarre defect received from China

In a number of articles before (e.g. this or this) I've written about the specifics of ordering from China.

In a nutshell it is unpredictable unless you have your people there, holding others at the Chinese equivalent of a gunpoint (maybe a gunpoint?).

One way to decrease those risks is to work with the same vendor and build mutual trust, educate them on how to avoid mistakes etc.

However even then you are not guaranteed.

We are working with the same vendor for many years now and have been together through a lot already.

Which did not prevent us from receiving a batch of STK795-821 ICs that had a problem we have never seen before: a shortage between the Vs input power (200V) and the IPM control logic driving power 15V (often labeled Vg).

Here is what I mean:

This is a picture of the bottom of a YSUS board 6871QYH053B which uses STK795-820 or STK795-821 or YPPD-J018C or YPPD-J018E etc.

I am enclosing that picture here so that you can easily see the groups of pins on the IPM.

We've sold over a 1000 ICs and repair kits and we've fixed probably just as much internally and I can easily say that 99% of all failures manifest themselves as one of the following:

• Short between Vs and GND pins
• Short between Vs and SUS_OUT
• Short between GND and SUS_OUT (I am actually not sure about this one, but it's worth checking)
• Diode effect (one-direction resistance) between VER1/VER2 (they're shorted out on the PCB) and ER_DOWN_OUT; normally there should be infinite resistance in both directions, but an internally shorted FET would leave a diode in the circuit between the two.
  The effect would be flashing on the screen.

A failed IC may also develop some other shorts, but rarely ever does or, more frankly, we rarely ever needed to search for clues other than the above.

Until last week when we received, in a box from a large batch of ICs, the following:

We've labeled the pins for you. There were 28 ICs with Vg shorted to Vs!

Unaware of that, we just processed normally a repair service for a board and proceeded to testing the result.

Bang, bang,
went PCBs,
and I assure you
bang, bang,
burned the TV...
Wait a minute, what you sold me there?
Wait a minute, that's a freakin' nightmare...
Bang, bang..

OK, enough TV pop folklore :-)

First, you should remember that resistance between Vg and Vs should always be infinite as shown below, only in both directions:

Second, you can bet that once you solder an IC that has a shorted Vg to Vs and test that in a live set, you will have A WHOLE LOT MORE damage than you originally started with.

For a starter, the ZSUS board's IC will also fail since it uses the same +15V that are produced on the YSUS board and dispatched, through the plasma logic board, to the ZSUS; but everything , or nearly everything, that is on the YSUS and feeds from the +15V will likely also be damaged.

This case is a great illustration of a few important takeaways:

1) You better know what you're soldering on a board; it won't hurt you if you test everything that you know tends to fail.

2) You are definitely better off buying ICs from someone who uses them versus someone who just imports them and sells them; you are not guaranteed unless said someone tells you they've tested the IPMs and they are honest, but you are , by all means, better protected if someone is working with the same material that you're going to be using.
We can't say with 100% certainty haven't sold a single IC of those to a customer, but chances are we didn't because we usually start using internally products from new shipments while continuing to sell the products from previous shipments - exactly for the sake of being first line of protection for customers.
Of course that is still not a 100% certain because , like in this case, only one and a half box out of twenty happened to be bad.

3) You can make a mistake even when working with a trusted vendor; that is because they themselves work with local vendors sometimes; of course that also means you would be better off being a first tier, but in many cases that is simply impossible.
Yet working with a trust vendor helps a lot resolve the problem and they would often times walk an extra mile to cushion any and all losses.

4) Maybe a bit strange for some, but for me this is a great illustration of why we should NOT warrant ICs once they are on a board. You see, a number of things can be bad on a board or in an IPM; to date I see some of my own technicians occasionally short two pins when soldering. Not those particular two, because they are quite apart, but certain other two are just sufficient.

The result would still be a failed board, sometimes filed buffer etc.

Any mistake - be it internal or induced - can cause a lot of damage.

A responsibility line must be drawn somewhere and I do not see a better place of running heavy current through the IPM.

We can't easily catch this particular case and the next best is just soldering the IPM on a board.

I'll finish this article with another two pictures for a different board we received from our vendor and the problem with it. The board was returned by a customer who claimed there were was a horizontal bar of about 1/8th of an inch that was dark no matter how may times he adjusted the plasma display ribbons to the connectors:

This is a Samsung Y-Main board LJ92-01601A used in Samsung PN50B450 and others.
It has an embedded YSUS buffer.

And this is what we found out upon careful inspection:

There was simply a cut through the PCB that has disconnected 4 tracks. This picture is made after we've removed the silicone, cleared the tracks and prepared them for connection.

The IC did NOT seem to have been reworked, but I can not see another explanation of how this could have happened.

Good luck in your own repairs!

Samsung FPT5084X/XAA with the BN44-00175A power supply cycles before coming on

I am publishing here, with a customer's permission, a problem related to a Samsung FPT5084X/XAA that both customer and we originally thought was the power supply board BN44-00175A, but turned out something else.

We repair BN44-00175A, but in this case pretty much all the work was done by the customer, so no credit to us for other than posting it publicly in hope it may help someone save time.


QUESTION 1

"Hello,

I have a FPT5084X/XAA with the PS BN44-00175A power supply. 

I bought and installed the capacitors repair kit from Coppell TV Repair (you guys)  and the same symptoms persist.

Symptoms:

panel works but takes quite a few self power cycles to come on. When it does this self on and off the plasma display is primed up when it comes on then you here a click and off, then a click click on eventually you will hear the chime and BAM! the panel comes on.

After the panel has been on and playing and warmed up it will turn on and off fine no issues. BUT if I unplug it for any amount of time it will go back and do the on off on off deal again. Same issue if I leave it plugged in and try turning it on well after its been on and playing.

There is NO issues with the picture it is very clear/sharp and looks great when working.

Trouble Shooting:

I have checked both the VA/VS voltages they are with in spec when the unit is on and playing.

I have visually inspected the PS board for bad cold soldier joints, I couldn't see any (but that doesn't mean I didn't miss em too).

I have repaired several Panels, my soldering skills are pretty good, but this Power supply has me stumped!

The panel has VERY low hours on it, around 5000.

I am interested in your BN44-00175A repair service if you think that will fix the PS, I don't think its an issue with any other board but with Plasma Panels it hard to tell sometimes!

thanks

-jeremy"

ANSWER 1

"See if you can manually activate the board (PS_ON to GND and VS_ON to +5V) and if it does the same strange behavior.

We have another (different) board here, which was sent with practically identical description as yours, but when we test it manually (that’s how we test most of the power supply boards – with artificial and not actual load in an actual TV set) – it works just fine.

So I wonder if you can repeat the problem with the power supply board alone which would give us something to work with."

 

QUESTION 2

"Will do, just to make sure, I am using a jumper wire from PS_ON to GND  and another Jumper wire from VS_ON to +5V and then I plug in the power cord?

I have done something similar for CCFL's to kick on, on non Samsung LCD tvs. 

And if this works, what does this mean?

Thank you Bobby for the quick reply!"

ANSWER 2

 

"Well it means we don’t have an easy way to reproduce the problem.

It may still be in the power supply board, e.g. it may show under specific load conditions which we fail to reproduce properly here, but it may also be a main board or plasma display controller, both of which affect the power on cycle."

QUESTION 3 (PROBLEM FOUND)

"Hi Coppell TV Repair,

just wanted to follow up with you on this.

So after doing some major troubleshooting and swapping out and testing other power supplies and main boards from compatible Sammy Panels who shared the same plugs.

Forcing the power supply to stay on the voltages were spot on perfect for VA/VS and others.

I found out and tracked it down to the main board not sending back the 5v to the PS,  The cause was the CPU and from the looks of it someone tried to reflow it at one point. If Pressed on the CPU sink or used a hair dryer the panel would fire up fine.

So main board replacement, seems to be common problem with these when they heat up around the CPU They sag pretty bad.  Guess I will need to put a support under it.

Anyway thought I would share what I found in case it might be useful for you.

Thanks for taking the time to help me out."

There, hope it helps!

P.S. As I told the customer I do not think that supporting the board - or pushing a processor - is a long term solution to the problem. It probably just needs reflowing. But I'll get into that another time.

LJ92-01490A repair question again

Question: 
 Dear Coppell TV Repair,

Just a question.
I have one of these sustain boards LJ92-01490A which was shorted.when I got the tv.
Both buffers were also shorted.
I bought a y sustain kit which consisted of all the transistors and diodes and three mosfets.
The tv would now turn on and stay on with no buffers attached.
Had all the right voltages.
I bought a used buffer on eBay and turned on the set and it immediately blew on of the buffer chips.
I have ordered two buffers and I guess my question is will the sustain if its on and working blow a buffer board or did I just get a ready to blow buffer.
My intentions are to send you all three boards to check but of course I would rather save the money.
I really am relying on your trustworthiness to tell me if a working sustain can blow a buffer board.
Thanks Gary

Answer:
OK, if you rely on our trustworthiness then read this carefully a few times because it may be somewhat confusing, but that's unfortunately how it is...it is complex.

1) A perfectly working YSUS board LJ92-01490A *can* and is known to sometimes damage perfectly working buffers.
In order for that to happen it will have to be fed improper signals by the plasma display controller.
A perfectly good YSUS, when fed proper signals, won't damage buffers, of course.
And of course the same is more or less valid for other plasma TV sets, but we've seen it happen with this one a bit more often than with others.


2) An improperly repaired YSUS LJ92-01490A *can* kill perfectly good buffers, even when fed proper signals from the plasma controller.

Knowing this particular board very well and knowing the SJ repair kit contents I am keen on making a statistically educated guess that some 20% to 30% of their customers for the kit would have an issue similar to yours. 



They just lack components in that kit that do tend to fail and when they do and don't get replaced they do cause exactly what you describe.

Of course there's no way for me to tell whether this is your case or if you have a bad plasma display controller or if you have yet another problem.

But I'll get to the question of what those components are a little further down.

3) I do not have an easy check for you on how you can test the plasma controller; it fails relatively rarely, but when it does it can very quickly turn a repair job into a financial cliff. I know that first hand.
So whenever I have the slightest doubt that it may be behind failures I tell customers - and would have told you if you've send us such boards - to have it replaced.
I have doubts based on the condition of the YSUS board when I first see it and the failures on it; in your case I can't do that, but if indeed BOTH buffer boards have failed I'd rather go for it.

4) While you can send all 3 boards you must be aware that we will not take them under our eBay listing as the YSUS has been worked on.

We'd only take it directly and we'd still offer no warranty. Only a video of it working in a set.

5) In the hundreds - yes, hundreds! - of LJ92-01490A boards we've serviced we've established that often times the problem is NOT on the board itself, but in how it was serviced before us.
There are several common mistakes people do when attempting to service that board and while I won't list here all of them for reasons I'll discuss in a minute I'll mention that one common problem is that people often tear the copper connection linking the top and bottom tracks on the board when they pull out the Vg filter capacitor (680 uF/25V or 35V -forgot which one) located near the power connector.

That leads to a board producing no image, which is not your problem, but illustrates my point.

In conclusion I'd like to say a few things.

First, no offense to SJ, but it is my opinion that a lot of their kits are simply sucked out of their fingers or, more likely, copied from other places. They are NOT based on first hand experience.
Of course that also allows them to have much more kits than companies like us who actually only release repair kits based on first hand experience.
Business-wise they are the smart people and we are the stupid ones.

Second, the above is also the explanation on why we do not want to disclose everything we know about repairing boards.

I personally stay late at night to reverse engineer, experiment, kill, repair and kill again a board before figuring out why it doesn't work the way it should.

I do not feel it fair - or reasonable - to post all of my findings only so companies like SJ or any coastal part distribution company can assemble a repair kit and start selling at a lower cost.

The value of what we do is in the knowledge we produce and the way we produce it - through hard work.

Of course, often times it gets out there, one way or another; but you'd be surprised how often it gets there incorrectly or partially (like with their repair kit).

Third, some issues are just too complicated to explain and fall under too many different cases to bother creating different repair kits and explaining which is for what; especially in the light of the risk of someone just copying the explanation and underpricing you.
Yet another argument is that a one-size-fits-all repair kit like the one SJ offers (for this case) is inefficient price-wise.
Their kit contains parts that you usually do not need, like the RJH3047 MOSFETs, which rarely fail, but it lacks other parts which you MUST replace when they fail.
Yet it contains 4 pieces 88N30W (or 88N30P), which you rarely ever need since they fail as a result of overload and it is worth to replace just the one or two that failed and not all four.


A universal repair kit would be highly expensive and highly inefficient, even when properly done. By "properly" I mean covering some 95% of all cases.

It would require reading and understanding and for those who manage to get through it the kit alone would become useless as they'd know which parts they need for what cases.

SJ apparently doesn't think so and , business-wise, they may be right and I may be wrong.

But that's how I am and that is how this company is run.

adsoft68's issues with capacitors, honesty and his own abilities

Synopsis: This article is our right of rebuttal and presentation of our view in the case of our eBay customer A. S. (full name preserved in accordance with US privacy laws) who left us a feedback stating

"Fake repair kit, thats are just capacitor the seller are not honest."

We present this in hope our  prospect customers would have the chance to first hand judge to the truth of the above statements as well as make better purchasing decisions.

History:

Step 1: A.S. (adsoft68 on eBay) purchased the following item on eBay:

REPAIR KIT FOR SAMSUNG BN44-00192A BN44-00192B POWER SUPPLY NOT COMING UP (#111283684871)

Purchased item was shipped and delivered accordingly.

Step 2: We received the following message via eBay (all messages are quoted without change):

"I bought this item from you, I was surprised that inside I find just 3 capacitor.
I never recognize on your description that CM... was capacitor.
In electronic capacitor have other name Volts and microfarad.
I am sorry but I dont need it for repair my tv. In most common cases are mosfets. I already replace all capacitors (no more than 3$ (your kit 10$)) how can I do for give you back and have my moneies? I never use the capacitors
Regards
A"

Step 3: We responded with the following:

"Send it back to the address on the envelope and include your eBay user name inside."

Step 4: We received the following from A.S., apparently after having left us the above negative feedback accusing us in dishonesty:

"Understand, i am not stupid, dear friend, the shipment fee are more than the value of item.... i prefer to get it in to garbage... At least i lost 37$ but you had one negative feedback .... I also claim to ebay your not honest business in fact you sell your capacitor like repair kit..isnt correct my friend, for repair the powerboard you need also some mosfet....."

Coppell TV Repair's rebuttal and thoughts:


My guess is that A.S. believes that we just put together a few capacitors and are selling that as a repair kit for whatever made-up problem.

This is, unfortunately, not an impossible scenario. I know for a fact that some companies in the business do it, but I'll get to that in another post.

So no issue with the customer suspecting us. I do, however, have an issue with a bold unsupported statement that we do sell a fake repair kit and are dishonest in the face of the following easily verifiable facts:

First, the kit has sold 18 times before A.S. placed his order and received at least 7 reviews from other customers; one such review clearly stated the kit did not help, the others said they were happy with it.

Don't take my word for it, take your time and find the reviews in our eBay feedback history!
Second, to the point of this kit NOT helping real life problems, there's actually a PICTURE in the listing showing the bulged capacitors causing the described issue! How much more of a proof you want that what is being sold does solve an actual problem?
That picture was personally made by me and the kit was assembled and listed AFTER we fixed a few such boards for the symptoms we describe and the components we include.

Third, everything advertised in the listing is exactly what is being sold; nothing is misleading and nothing is dishonest. Do not take my word for it - open the listing and read:

"Kit contents: CM856, CM858, CM861 replacements. More may be added over time if we hear from customers who have other bad capacitors on the board. All components in the kit are with same or better quality compared to the OEM parts used on the board."

If you find our listing or responses dishonest PLEASE let me know why!

Further, A.S. seems to have an issue with the repair kit containing ONLY capacitors.

This is what we have seen to be bad and nothing else. This is what the kit contains.
It is not only possibly, it is very common for electrolytic capacitors to go bad rendering a board - not just power supply board - useless. There hundreds of companies and probably thousands of repair kits made ONLY of capacitors.
Do not take my word for it - check badcaps.com for a starter, then just google for "capacitors repair kit" and you will find tons and tons of different ones!
 
Which begs the question: what else should it have contained to make A.S. happy? A few MOSFETs? What if A.S. had a blown transformer? Or a few diodes? Or a blown fuse? What about the ICs on the board?
 
What would have A.S. or someone else said if they received a bag of parts most of which were not bad?

It's a rhetorical question the answer to which we still hear every now and then even though we try to make our repair kits dedicated to a single problem: a customer would come back asking credit for the part of the kit they did not need using.

Most important of all: 

Where is the problem here: in our representation or in customer's inability to make use of it and, related, in his unjustified expectations?

What do you think?