Samsung PS50A plasma screen issue

[DeThaey]

Hi all,

I'm hoping to get some of your insights with regards to a strange screen issue I'm seeing on my Samsung PS50A plasma screen. It worked fine when I last turned it off, but yesterday when I turned it on, it went straight to a weird screen, which I would describe as "black and white only, with random horizontal black lines across the screen, in more or less fixed positions". I still have sound, and the TV is still responding well to the remote. You'll find attached some pictures for your reference... Note that I do have some color when I switch to a channel without signal (see attached picture).

Maybe good to know is that we just had a few hot days outside (30+ degrees) where I live, and the TV is standing directly in front of a window. It's the only external influence I can identify at the moment, that could've caused something.

I've read the plasma troubleshooting guide, but unfortunately didn't find a conclusive answer (yet). I've done the following so far, with no results:

- Issue persists on all channels and input sources
- Power cycled the TV multiple times
- Verified fuses on the X sus and Y sus boards
- Reseated the main connectors between the different boards
- Visual inspection with back panel removed - I found one slightly bulged cap on the X/Z sus board, but I'm not sure it might be causing the issue?

Any ideas or suggestions are welcome! Thanks a lot!

[tom66]

Re: Samsung PS50A plasma screen issue

This fault is likely X-main. That cap is very bad. Have you checked if the fuse near the cap (green thing) is OK?

[DeThaey]

Re: Samsung PS50A plasma screen issue

Tom, thank you so much for your prompt reply.

I did not check the fuse before, but I just grabbed my multimeter and the fuse seems blown. Do you reckon I can buy a replacement fuse + cap in my local hardware store, and it will solve the issue? Or do you think the board in its entirety is busted? I've attached a closer picture of the X main board, in case it helps. It all looks quite good to me, except for the buldging cap...

[tom66]

Re: Samsung PS50A plasma screen issue

I think it's worth a shot to replace the fuse and cap. If it does blow the fuse again you will probably have to do a more in depth repair or replace the whole board.

[DeThaey]

Re: Samsung PS50A plasma screen issue

Hi Tom,

I replaced the cap and fuse, but the issue persists unfortunately. No improvement noticed... One thing I noted is that the fuse is fine now, i.e. it didn't blow again immediately after switching on the system again.

Do you have any more suggestions about what I could try more? I'm ready to try a more in depth investigation in case you do. I have access to probably whatever tools I'd need. Are there any volt measurements on the X-main board that could help pinpoint the faulty part of the board?

[DeThaey]

Re: Samsung PS50A plasma screen issue

Does anyone have an idea what else I could try? Thanks!

[tom66]

Re: Samsung PS50A plasma screen issue

Can you see a Ve test point on the X-main? What does that test at?

[DeThaey]

Re: Samsung PS50A plasma screen issue

Hi Tom, I'm measuring 100.6V at the VE test point...

[DeThaey]

Re: Samsung PS50A plasma screen issue

Anyone any further ideas? Does the Ve voltage (100.6V) seem alright to you?

[tom66]

Re: Samsung PS50A plasma screen issue

That Ve voltage is good.
Can you test the transistors on the heatsink on the X-main -- do you know how to test them?
Do you have access to an oscilloscope?

[DeThaey]

Re: Samsung PS50A plasma screen issue

I don't have immediate access to an oscilloscope, however I might be able to use one at work...

How big do you estimate the chance it's related to X-main? I found some used/refurbished boards on Ebay for about 40 euros...

[tom66]

Re: Samsung PS50A plasma screen issue

There is a small but non-zero chance the control board is causing this, as we had a very old Samsung plasma on here with all the symptoms of a bad X-main.

In the end it turned out a small SMD resistor on the control board was open circuit, so the X-main was receiving the incorrect control signals. One in a million occurrence though.

I'd say X-main is a fair bet. Really you would need to test the X-main installed in the set so you'd need to be able to borrow the scope.

[Atlascopco]

Re: Samsung PS50A plasma screen issue

I have the same problem (posted separately here: https://www.badcaps.net/forum/showthread.php?p=467280). I've replaced the XMain but to not avail. The problem remains exactly the same.