50ux58b plug it in green leds power up & then go out

had it repaired by service tech. was in the high voltage circuit. small part , & about 20 minutes time & he had me up & running for 240 bones. I'm sure it was a 50 cent part, oh well, it's a great picture.

Working on a 60UX54B with identical problem (also has the same power supply as yours) which failed from power surge.

Can hear a quiet squealing sound when plugged in for about 2-3 seconds illuminating 6 of the 8 green power monitoring LEDs, actually powering up high voltage and audio and then shuts down. No other activity or response from power button or remote. +5VDC and +9VDC LEDs remain dark as no powerup command is sent by TV CPU which is normal. +12V standby LED does illuminate and then turns off with rest of LEDs. Is this +12V standby LED supposed to remain on at all times?

Red 'protect' LED illuminates dimly during this brief power-up time, gets bright and then intermittently flashes (very dimly) of all things after shutdown. There is no flash diagnostic feature for this LED. Vcc (pin 5) of PWM controller (I901) on PCB fluctuates between 14-21 VDC in sync with flashing of red "protect" LED.

No shorts or excessive loads in other parts of TV because no difference when power PCB is disconnected from the audio/tuner PCB. Still powers up for 2-3 seconds when plugged in and then off. LED's stay on much longer as there is no loads on power supply other than the LED's themselves.

All IC protectors test good.

So now I suspect STR-6811A (I901) PWM controller is at fault and it would indeed be damaged by a power surge. This is the 7 pin IC on the large heatsink near the switching power supply transformer where AC cord connects.

Ordered a replacement STR-6811A on ebay ($12.00 with shipping) and will update here if it solved my problem.

bad power supply