Power but no picture Samsung plasma 42" PS42C450B1WXXU

[Milasmith]

Re: Power but no picture Samsung plasma 42" PS42C450B1WXXU

Thanks for all the help. I'm going to try and track down where the fault is. Is it ok to test capacitors in situ or do they need removing? My meter doesn't have a capacitance function so was going to test the resistance across them and see if it quickly rises to infinite.

[tom66]

Re: Power but no picture Samsung plasma 42" PS42C450B1WXXU

I wouldn't worry about capacitors - the ones you can test at least will not tell you much, and failure of those is unlikely to cause your fault.
Just test transistors for now.

[angelos]

Re: Power but no picture Samsung plasma 42" PS42C450B1WXXU

I had a similar case as yours and the mosfets on the "secondary" side, if you can call it that, were shorted. They are the one's responsible for supplying that voltage for the buffers. From the Vs supply side those mosfets on a separate heatsink were ok thus no short could be detected on the Vs line.
Normally a lot of dry joints on the soldered points of those mosfets that caused the issue. Check carefully.

[tom66]

Re: Power but no picture Samsung plasma 42" PS42C450B1WXXU

I had a similar case as yours and the mosfets on the "secondary" side, if you can call it that, were shorted. They are the one's responsible for supplying that voltage for the buffers. From the Vs supply side those mosfets on a separate heatsink were ok thus no short could be detected on the Vs line.
Normally a lot of dry joints on the soldered points of those mosfets that caused the issue. Check carefully.

Yes those would probably be the PASS FETs.

https://cdn.badcaps-static.com/pdfs/...9b9b8fbd9f.pdf

page 11

Though the circuit on the Samsung PDPs is considerably simpler nowadays, due to cost reductions and efficiency improvements.

[Milasmith]

Re: Power but no picture Samsung plasma 42" PS42C450B1WXXU

Thank you so much for all the help. I've been waiting till I could afford to get the parts. Finally fitted a Y main and X main and the TV is working! Thanks again

[Milasmith]

Re: Power but no picture Samsung plasma 42" PS42C450B1WXXU

By the way, I tested the old boards every way I could think of and got identical readings to the working replacements so I never did actually narrow down exactly which component(s) failed.

[tom66]

Re: Power but no picture Samsung plasma 42" PS42C450B1WXXU

Glad to hear the set is working.