Samsung PL51E8000 - Everything works but video.

[plpsanchez]

Hi, everyone!

I had a fried Y-main (Y-SUS) board.

At first, I replaced Y-buffer and Y-main, then found that the new Y-main had a partial short circuit (50 ohm) from VS to GND, so replaced this boad again. Replaced also X-main, although I had no evidence of problems with it.

But I still have problems because the TV does not turn on.

To trick the logic board, I disconnected the cable that goes from Y-Main to the logic board (see red arrow in the attached picture).

With that cable disconnected, everything works, except for the video. Even voice commands are working.
In this situation, SMPS, Y-Main and X-Main voltages were checked and are all OK.

If I reconnect the cable, the TV powers off as soon as I try to turn it on.

Any suggestions on what the problem is and on what should be done next?

[drussell]

Re: Samsung PL51E8000 - Everything works but video.

To trick the logic board, I disconnected the cable that goes from Y-Main to the logic board (see red arrow in the attached picture).

With that cable disconnected, everything works, except for the video. Even voice commands are working.
In this situation, SMPS, Y-Main and X-Main voltages were checked and are all OK.

You really get all four of the high voltages (Vs, Va, Ve, -Vscan) with the flat ribbon cable disconnected?
Interesting.
That's different behavior than the ones I've been working on but they are a totally different design, so who knows.

What happens when you do the logic board test (by shorting the two highest pin numbers, usually 3-4, on the test jumper on the logic board) with everything except the main board (input connector board) connected and jumpering the PS-ON to ground manually?

If you have all high voltages and the logic board test does nothing, I guess I would suspect the logic board.

Do all the high voltages come up to full voltage briefly with the Y-Main connected to the logic board?

[plpsanchez]

Re: Samsung PL51E8000 - Everything works but video.

You really get all four of the high voltages (Vs, Va, Ve, -Vscan) with the flat ribbon cable disconnected?
Interesting.
That's different behavior than the ones I've been working on but they are a totally different design, so who knows.

Yes, I do get all of them. Perhaps THAT is a clue .

Do all the high voltages come up to full voltage briefly with the Y-Main connected to the logic board?

Yes, they do!!!

I was going to check the logic board, as you suggested, but know what? When I'd put the cable back I noticed a small particle of something dropping to the floor.

Was it dust? Solder? Metal fragment? A gremlin ? I did not find it, so I do not know what it was.

But now the TV is working. Let's be thankful and just see if stays that way.

Thank you for your support.