SUMMARY
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This is a Vizio VO42L. It won't power on. When the TV is first plugged in the VIZIO logo should be orange. When the TV is turned on the logo should change to white. Instead the logo is always white and unaffected by the power button. The logo is flickering as it appears to struggle to have stable voltages and "boot up".

THINGS TESTED
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1) Followed troubleshooting section of service manual (thank you for uploading these on this site!)
2) +5VSB is working fine and does not fluctuate
3) U22 (1117 regulator)...

Re: Vizio VO42L will not come on

Huge thanks to you dgtech and plainbill.
I wound up buying a new main board which fixed my issue.
Now I'll be able to watch Thanksgiving day football in the basement next to my keg fridge!

Thanks a ton.

Re: Vizio VO42L will not come on

I see no backlights. Even with a flashlight I don't see anything.
I can't seem to get pictures that are clear enough to read the writing... Will try more tonight. Here is the voltages on the LDO's when the tv is "on" (Vizio emblem turned white). 2 of them don't have input voltage so they obviously aren't regulating but the others seem fine...

LDO's:
U19 G1117 (pin 1 gnd, pin 2 VO, pin 3 VI)
2 - 1.24
3 - 3.85

U21 G1117 (pin 1 gnd, pin 2 VO, pin 3 VI)
2 - 1.24
3 - 2.5
...

Re: Vizio VO42L will not come on

Any ideas dgtech or plainbill?
I've been checking the diodes and fuses on the mainboard but everything seems okay. Should I just replace the mainboard or could it be a different board? The geeky engineer in my really want to try and repair but I'm just not sure where to start.
The reason I think it's the mainboard was from plainbill's post in this thread: [URL="https://www.badcaps.net/forum/showthread.php?t=17001"]https://www.badcaps.net/forum/showthread.php?t=17001[/URL]

Thanks in advance!

-...

Re: Vizio VO42L will not come on

Little more info... Please let me know if anything else would be helpful... I was going to post better pics once the board problem is a bit more clear.

After reading through all the Vizio posts I saw a lot of references to U33/AMC1117. U33 is an 8 pin chip on my main board so I dismissed that.

F1 and F2 on the main board checked out fine.

TV screen stays completely black when I turn the tv on.

Caps all looked good.

Here is a picture of the overall back of the tv:...

The Vizio emblem is in orange, and turns white when I hit the power button.
On the power supply I have observed that +5VSB is at 5V, PSON is at 0V, and stays there when I hit the power button, A1 is 3.3V when "on", B1 is 5V when "on", otherwise A1 and B1 are 0V. Does that mean the problem is with the main board?
I unplugged the inverter board which had no effect.

What do I need to do to start troubleshooting the main board (assuming that's what the above symptoms point to)?...