Samsung PN50B430P2DXZA

[ned1]

Need help with 50" plasma. At beginning it will not pique up. Found shorted X-main board. Repaired board and it powers up ok. All voltages per panel sticker ok. But the picture looks fuzzy. Removed power cabke from power supply to main board, shorted ps-on to ground and put jumper on 3-4 on t-con. Test pattern came but fuzzy again. Ordered another t-con and X-main , still same problem. Please see attached picture.

[tom66]

Re: Samsung PN50B430P2DXZA

Can we see a picture of the fault?

[ned1]

Re: Samsung PN50B430P2DXZA

See picture

[tom66]

Re: Samsung PN50B430P2DXZA

That is an X-main fault if I ever saw one...
Can you see if you can find the Ve voltage and try testing it?

[ned1]

Re: Samsung PN50B430P2DXZA

88 volts, I repaired one x-main and purchased another one.

[ned1]

Re: Samsung PN50B430P2DXZA

Both have same problem.

[tom66]

Re: Samsung PN50B430P2DXZA

Check the ribbon cable between X-main and control board is not damaged in any way.
Do you have an oscilloscope available for testing the panel drive waveforms?

[ned1]

Re: Samsung PN50B430P2DXZA

I can get one but you will have to send me instructions what to look for.

[tom66]

Re: Samsung PN50B430P2DXZA

That's fine just post a picture of the scope. You will need a 10X probe too.

[ned1]

Re: Samsung PN50B430P2DXZA

There is another voltage check that is on Y main board VSCH. It reads -44 Volts. The VSC reads -193 which is correct by panel label. What is VSCH supposed to read, it's not labeled on the panel sticker.

[ned1]

Re: Samsung PN50B430P2DXZA

Does anybody knows how to check voltages on VSCH. The VSCH to ground measure -44V steady. VSC scan is -193V steady. The reason I moved to y-main board is the sparks I can see sometimes on plasma screen.

[ned1]

Re: Samsung PN50B430P2DXZA

Here is the picture of Y-systain

[Glitcher]

Re: Samsung PN50B430P2DXZA

It could be the power supply, I had a similar model with a problem that kind of looks like that with similar parts. I swapped out 2 new x-mains and the problem was the same.

After swapping everything, it turned out to be the power supply. Wasn't sure for the reason why, but it worked.

https://www.badcaps.net/forum/showthread.php?t=32175

[ned1]

Re: Samsung PN50B430P2DXZA

Thanks a lot. This one is driving me crazy, I am about to loan scope and start messing with it. I would never suspect bad PSU since all voltages are so steady. I will look into PSU and let you know.

[tom66]

Re: Samsung PN50B430P2DXZA

Vsch is Vsc + about 130v to 160v in your case it's OK.

[ned1]

Re: Samsung PN50B430P2DXZA

OK VCS scan to ground is -193 but VSCH to ground is -44. I just want to confirm with you again. I did not measure VSC scan to VSCH. Is that needed.

[Alastair E]

Re: Samsung PN50B430P2DXZA

Best start again.

Measure All the voltages in the set, those from PSU and those on Y/X-sus boards, List them here--with their circuit references, like Vs, Va etc....

For such an extreme fault, I'm guessing one is a fair bit off....

[tom66]

Re: Samsung PN50B430P2DXZA

OK VCS scan to ground is -193 but VSCH to ground is -44. I just want to confirm with you again. I did not measure VSC scan to VSCH. Is that needed.

You can see the difference is 150v it is fine. Your problem likely xmain or fault with control board

[ned1]

Re: Samsung PN50B430P2DXZA

All panel sticker voltages are correct. I did not check low voltages but VS, VA, VSC and VE are exactly what panel sticker suggests. I had blown X-main, had bunch of blown Fets, replaced them all and got bad picture. I purchased another X-main same problem exactly, purchased another control board same problem exactly. I did remove main board and run test pattern by shorting PS-on to ground and putting jumper on control board pin 3-4 and 4. Test pattern look bad also, it loaded test pattern went try diferent colors and paterns but picture was bad. I am checking right now Y-sustain cantfind anything bad on it at all. I guess next will be checking power supply as Glitcher sugested and trying to get scope hooked up and get some education how to use scope.
I appreaciate all your help guys.

[ned1]

Re: Samsung PN50B430P2DXZA

Got the scope , hooked up to y-main board.
Please see picture and tell me if I am doing it right?