PN50A550 no video

[ajshoe]

Have a Samsung PN50A550 plasma that turns on by clicking, audio chimes on, but no picture. can turn set off and audio chimes off

PS_ON is 4.4V - turn set on goes 0.3V
VS_ON - 0V set on or off

VA = 57V
VS = 0V

replaced C102 on Main board. Have tried removing individual cables to ysus & xsus boards - still turns on (relay clicks)

seems like a bad main board.

[ajshoe]

Re: PN50A550 no video

finally got to the problem with this set. wasn't main BD. Actual first problem was Ysus BD. fuse was blown on it. replaced it and tried forcing set on. Unfortunately when I did that I jumpered PS_ON on wrong conn ON SMPS (Logic BD cable). This fried the SMPS. Repaired that, main BD, and now waiting on Ysus new board. ysus board has several Mosfets blown - not worth fixing old one.

[ajshoe]

Re: PN50A550 no video

completed SMPS repair. turned out Main BD was OK. Ysus was definitely bad. put it back together and had to force set on. LOGIC BD was bad. new logic BD and set has great picture. Sammys are one of the worst sets to fix - usually more than one board is toast when set it goes south.

[Alastair E]

Re: PN50A550 no video

completed SMPS repair. turned out Main BD was OK. Ysus was definitely bad. put it back together and had to force set on. LOGIC BD was bad. new logic BD and set has great picture. Sammys are one of the worst sets to fix - usually more than one board is toast when set it goes south.

I wouldnt say so.

Sounds to me you killed a load of stuff by Forcing the PSU on (and making error doing so) when there was a shorted Y-SUS.....

Why do you think it cheaper to replace Y-SUS instead of repairing original?

MOSFETS Aint THAT expensive!

[ajshoe]

Re: PN50A550 no video

pretty sure logic board was dead on arrival. but your right I messed up the diagnosis pretty good. figured out the bad Mosfets on Ysus BD - how do u get those out ?? I have solder socker but it seems useless on these. do u have a cross for RJH3047 ?? seems only avail form CHINA