Vizio P75-F1 TV shows logo then goes black. Repair help!

[Hybrid Divide]

I have a Vizio P75-F1 with the infamous black screen of death.

 

The TV powers up, shows the Vizio logo like normal. Then the picture goes black, but the backlight remains on.

 

When doing a factory reset, (Hold Vol Down + Input for 10 sec, release Vol Down and continue to hold Input). The TV will reboot multiple times, but nothing changes.

 

This has happened a few times since I got the TV, but always managed to snap out of it relatively quickly until now.

 

Been at this several weeks now. On my 3rd replacement Main Board.
First one showed the Vizio logo, then went black, but unlike the original, the backlight turned off.
Second was totally dead. Couldn't even get the logo to display.
Third board acted exactly like the original board. (Vizio logo, goes black, backlight stays on.)

 

Two replacement Power boards don't seem to have any effect.

 

A replacement T-Con board didn't seem to have any effect either.

 

I have not replaced the LED driver board, as the Flashlight test reveals nothing. And I know the panel is good, as the Vizio logo is displayed normally when the TV first boots. And yes, I did mix and match several of those boards before sending them back.

 

Do you have anything you can suggest? I have a multimeter, but I admit I'm not very familiar with checking voltages. Things like knowing what setting I should set the multimeter to, and what spots to check would be great to know. Pictures would be a bonus.

 

EDIT: I ended up buying a whole new set of boards (Power board, T-Con, LED Driver, and Main board) on ShopJimmy with zero luck. Same thing.  Again, when it powers up, the logo comes up fine.  Backlight too.  So I'm sure the panel is fine.  But I've literally replaced everything else, and I have NO IDEA what else it could be.  There's no way I got that many dud boards.  Please help!

 

EDIT 2: Tried reinstalling the firmware, but it never seems to get the point that it's reading the data off the USB drive.

[WkdPaul]

* thread moved to the Troubleshooting section*

 

Please be careful where you create your thread.

[Hybrid Divide]

1 minute ago, wkdpaul said:

* thread moved to the Troubleshooting section*

 

Please be careful where you create your thread.

Understood.  Thank you!