LG 50PK950-TA Plasma TV with Audio - But no Video

[MrBig9529]

Hi All,
Please advise me on how to proceed on this repair.

LG 50PK950-TA plasma TV with Audio - But no Video/picture/display, with Power. Can increase/decrease the volume. No brightness seen even in a dark room.

Recommended Readings as per Sticker:
VS = 203V
VA = 60V
5V = 5V
-VY= -190V
VSC = 150V
VZB = 108V

Actual Readings (WITH TOP and BOTTOM buffer boards)
VS = 201.8V
VA = 60.0V
5V = 5.07V
-VY= -12.9V
VSC = 13.9V
VZB = 108.4V

Actual Readings (WITHOUT buffer boards)
VS = 201.8V
VA = 60.0V
5V = 5.07V
-VY= -.9V
VSC = .3V
VZB = 108.4V

Actual Readings (WITH UPPER buffer board)
VS = 201.8V
VA = 60.0V
5V = 5.07V
-VY= -12.3V
VSC = 13.1V
VZB = 108.4V
Actual Readings (WITH LOWER buffer board)
VS = 201.8V
VA = 60.0V
5V = 5.07V
-VY= -12.3V
VSC = 13.1V
VZB = 108.4V

I concentrated in the Y-Sustain board as the VSC and –VY readings are abnormal (and this is the common cause for ni video symptoms as per readinds) though I haven't found any faulty big resistors, no blown FUSE, no swollen capacitors, no bad transistors/FETs. Tried to resolder the possible cold soldered connections but still the same. I need more ime to check those surface mounted parts.

Is this a confirmed Y-Sustain board problem? Any hint on repairing this Y-sustain board?

Thanks in Advance

[MrBig9529]

Re: LG 50PK950-TA Plasma TV with Audio - But no Video

just to add in, i forgot to mention that i also tested both buffer boards. No shorted pins (connector going to the orange cables going to panel) with respect to V+ and Gnd point.

[MrBig9529]

Re: LG 50PK950-TA Plasma TV with Audio - But no Video

just an update. I tried to do the pattern test and didnt get any display.

Upon searching, i found this post ( though different problem),

https://www.badcaps.net/forum/showpo...53&postcount=1

I message the guy who has the spare boards if i can buy his Y-sus board, and yes - he even asked me to take his card and test first before buying. After the Y-sus board replacement - my TV is now working. Thanks to bro SandTang !!!

[MrBig9529]

Re: LG 50PK950-TA Plasma TV with Audio - But no Video

Hi Guys,
TV still running fine. I am eager to repair my faulty Y-sus board as my spare, Anybody have some pointers on what is wrong on this Y-sus board? anything that i need to check further? No faulty big resistors, no blown FUSE, no swollen capacitors, no bad transistors/FETs ( i even removed the FETS from the board to test properly. Tried to resolder the possible cold soldered connections but still the same.
Any input will be highly appreciated... Thanks in advance...

[monte8585]

Re: LG 50PK950-TA Plasma TV with Audio - But no Video

I have a 50PK450 LG plasma with just sound. I replaced the upper buffer after discovering that screen (bottom half) would come on when the top buffer was disconnects (had another lg plasma that had the same exact symptoms and replacing the top buffer only fixed it). I was wondering if I can now get away with now just replacing the y-sus and not harming the new buffer. I have replaced all 3 in the past (minus the other lg recently) and would not want to go in circles killing boards.