Fault Diagnosis Help - Samsung PS42Q97HD

[Mattyd893]

Hi, I need some help diagnosing the fault on my Samsung PS42Q97HD Plasma TV.
The fault occured some time ago and it's been sat in the spare room since, the TV just powered off and when it was switched back on the display was like this:
Samsung TV - YouTube

Need to know which board is the likely suspect for a quick repair, I can easily swap out the board and make voltage adjustments, just need pointing in the right direction a I cannot find info on a similar fault. I can also make component repairs but not really that interested in this case, just want to repair and get rid, failing that, if the faulty board is identified, i'll happily sell the remaining boards or TV as spares/repair.

TV has sound, just the pic is as shown in the video.

Thanks in advance!

[tom66]

Re: Fault Diagnosis Help - Samsung PS42Q97HD

Most likely Y-sustain. Disconnect one buffer (if it has two) and see if the problem still shows.

[Mattyd893]

Re: Fault Diagnosis Help - Samsung PS42Q97HD

So, think I found the problem after a closer look, the Y-Buffer or Y-Drive as some people call it seems to have a burned out chip:


Looks even clearer in the picture, took me ages to find it with just my eyes!

Is this likely to be simply an error with the board, probably due to heat, or is it likely to be a symptom of another problem?

[tom66]

Re: Fault Diagnosis Help - Samsung PS42Q97HD

So, think I found the problem after a closer look, the Y-Buffer or Y-Drive as some people call it seems to have a burned out chip:


Looks even clearer in the picture, took me ages to find it with plain site!

Is this likely to be simply an error with the board, probably due to heat, or is it likely to be a symptom of another problem?

More than likely that buffer has simply "had enough". Temperature kills chips. A cascading failure inside the IC (thermal runaway) probably led to latch up, putting 385V directly across parts not intended to have such, very quickly smoking it.

If you are skilled with a soldering iron you can confirm it is the buffer chip. Removing the chip is possible by cutting away the epoxy with a flat head screwdriver and then using a bit of solder wick. You should then get a picture with a black bar corresponding to the chip that has failed.

It's sometimes possible to source a replacement chip but I don't usually bother, a new buffer is maybe 10-20% more than an individual chip.

[Mattyd893]

Re: Fault Diagnosis Help - Samsung PS42Q97HD

More than likely that buffer has simply "had enough". Temperature kills chips. A cascading failure inside the IC (thermal protection) probably led to latch up, putting 385V directly across parts not intended to have such, very quickly smoking it.

If you are skilled with a soldering iron you can confirm it is the buffer chip. Removing the chip is possible by cutting away the epoxy with a flat head screwdriver and then using a bit of solder wick. You should then get a picture with a black bar corresponding to the chip that has failed.

It's sometimes possible to source a replacement chip but I don't usually bother, a new buffer is maybe 10-20% more than an individual chip.

I am skilled enough with a soldering iron and may give this a go just to confirm, but after removing it the board will need replacing again anyway. One question though, just for my own knowledge, why 6 Y-buffer connectors and 8 chips?

[tom66]

Re: Fault Diagnosis Help - Samsung PS42Q97HD

I am skilled enough with a soldering iron and may give this a go just to confirm, but after removing it the board will need replacing again anyway. One question though, just for my own knowledge, why 6 Y-buffer connectors and 8 chips?

Each buffer probably drives 96 lines (pretty standard) and there are 128 lines per Y connector, giving a vertical resolution of 768 pixels. So you should have a 96 line bar in the middle of the display.

[Mattyd893]

Re: Fault Diagnosis Help - Samsung PS42Q97HD

Thanks for the help, now to find a new board!