Sylvania lc370ss8m dead as a doornail

[mykolas]

My personal set developed a white picture and channel is frozen. I replaced the main board and all was fine. Two days later the set was dead. No red indicator light. Opened set, fuse, fusible resistors, caps all checked good in the two power supplies. Put the original main board back thinking that went bad, but same issue. Checking voltages I found 166v(hot ground) to the drain of Q501 where the schematic says it should be -3v. IC501 #6 VDD should be 16v but I found it fluctuating between 9-10v. All other voltages on this ic(power controller) are missing or extremely low.
I thought this would be easy, but I can't seem to get my brain around the problem.
Need some insight and direction.


Mykolas

[dskall]

Re: Sylvania lc370ss8m dead as a doornail

Need good clear straight on pictures of back of tv with cover off and each board.

[mykolas]

Re: Sylvania lc370ss8m dead as a doornail

Sorry it took so long to get back to this problem (many shootings in my neighborhood in Chicago) I had to move the family elsewhere.

To make a long story short, I traced and found 3.3v standby voltage changing value from 2.7v to 3.1v whenever I measured it. Checked the 3.3v line to the power transformer and found nothing wrong, No leaky diodes or bad caps. Applied a bit of heat to Ic637(3.3v regulator) and the set began to work.
Checked good out of circuit but under load started to break down.

All fine now,


Mykolas

[dskall]

Re: Sylvania lc370ss8m dead as a doornail

Thanks for follow up. Glad your tv is again working and family is safe.