Vizio LED TV will not turn on.

[Josue]

Hello, I have a Vizio LED TV Model #: M3D460SR, for some reason it went off and it would never come on again.
The "stand-by" light was on until I decided to unplug the power cord, leave the TV deenergized for about 2 minutes and plug it back in. after that, no more signs of life from the TV.
I opened the TV, and found three different boards, the PSU (715g4565-p02-w20-003h), the Main Board (715G4404-M01-000-005K) and the LED Driver Board (715G4863-P02-000-004S).
My first guess and hope was that the fuse to the PSU was blown. Negative, the fuse is good.
Visually and carefully inspected the PSU board looking for any blown capacitor, burnt smell or heat presence signs and found nothing. Using my meter (Fluke 87 V) measured the input AC Voltage (~120V) and measured the voltage at the pins of Conectors CN902 and CN903 (see attached pictures) and found +24Vdc, +12Vdc, and +5Vdc using the metallic plate as reference or negative.
My question here is: what voltage should I expect ath the pin labeled PS_ON? I measured 1.8 Vdc.
Or even better, what board would you change? I highly doubt that the PSU is the bad one, What is PS_ON??? is it the feedback signal from the Main Board to confirm that it is in fact getting power???
Thanks in advance!

 

[Harald Kapp]

Welcome to our forum, Josue.

+24V, +12V and +5V sounds like the power supply is in good order.
Maybe a dumb question: you have tried both the power button on the remote and the one on the TV, have you?

This discussion of the same problem may help you along in analyzing the cause of the problem.

 

[Josue]

Welcome to our forum, Josue.

+24V, +12V and +5V sounds like the power supply is in good order.
Maybe a dumb question: you have tried both the power button on the remote and the one on the TV, have you?

This discussion of the same problem may help you along in analyzing the cause of the problem.

Hallo Harald, danke.

I have tried both the power button and the remote without any luck, and from the badcaps forum that you pointed at, I get that PS_ON is coming from the main board and should be 1.85V at all times but when the power button is pressed.

I will push the power button 10 times today while measuring at the PS_ON pin, and expect a change of state (1.85V to 0.3V).
If I don't see a change, my guess will be that the main board is faulty, because is not sendig the signal to the PSU to react, and I will order the main board on line.

Thank You again Harald!

 

[Harald Kapp]

Before you order a new main board, you can make an additional test by short-circuiting the PS_ON pin to GND (by momentarily tipping a short piece of wire from PS_ON to GND) to see whether the board reacts to the PS_ON signal at all.