Question Vizio TV Blank Screen has stable 5v standby pin BUT 12v pins all read 19v

[haparaider]

The TV is a Vizio D55U-D1. The screen will not come on, but the white LED indicator does come on. It lights up, fades, sometimes blinks, and eventually turns off. It also sometimes comes back on after a few minutes. The screen always remains blank. I have tested several things inside the TV with a multimeter and have found that the power board is putting out a stable 5v at the standby pin that is connected to the main board. The corresponding pin on the main board also reads 5v. On the same connector, the 3 or 4 pins that are labeled 12v on the legend all read 19v on the multimeter. The only other discrepancy I can find (with my low skills) is the connector that goes from the power board to the LED driver board that is labeled at 24v is only putting out 22v when the TV is switched on. I have already replaced the main board with no change, so I don't think it's that (unless multiple things broke at the same time). Could something busted on the power board have caused the 7v increase and 2v decrease for those pins? And would that cause the TV screen to remain blank? Thank you for any suggestions.

 

[Akruser47]

I am having the exact same issue as you with a d50u-d1, I'm assuming the only difference between the two TV's is screen size, all internals must be the same. If you figure it out please let me know and I'll do the same. I'm beginning to get suspicious on if the power board replacement I received was defective as well because I have replaced every board and still nothing. I've replaced the main board, LED driver board, tcon board and the power board.

 

[haparaider]

Your power board is also reading a higher number for the 12v pins? Is it 19v or something around that? Did it do that before and after you swapped out the power board? I just ordered a replacement power board from ShopJimmy which should arrive later this week. I'll let you know if that does the trick and if the voltage is reading 12v like it's supposed to.

 

[Akruser47]

Yup 22V on the 24V pins and 19V on the 12V pins, the pson voltage is 3.7V so I assume that's fine

 

[haparaider]

I'd be curious to know what the voltage of a brand new working tv is. Maybe they're all 19/22v and it's not a power board issue. But we both swapped out the main boards too, plus you did all the other boards. Hopefully you got a dud power board, like you suspected, and mine will test at 12v when I install the "new" one. But I am beginning to think I am just the owner of a really expensive big dark mirror.

 

[MikeBY]

Sounds like a corrupted firmware update.
My PQ55-F1 did that when I first brought it home. Did a software update immediately after connecting to the Internet, with an automatic restart. It never recovered. It would power on, black screen, sit, and eventually restart itself, doing the same thing.
Factory repair replaced the mainboard, but it took a week. They had zero stock for an exchange at the time.

 

[haparaider]

So I swapped out the power board and the main board today for replacements from ShopJimmy and the TV turned on for about 5-10 minutes before going black again. I haven't been able to get it back on since then. It was on long enough to go through the tv set up, sign on to my WiFi, and sign into Netflix. Once I clicked a show on Netflix, it loaded then went black, with the audio playing for a few seconds before that cut out too. Maybe my video settings were too high and when it tried to show video from Netflix, it was too much to handle. Any ideas on how to get it back on so I can try and change my video settings? I've tried power cycling it but I'm back to getting just a black screen.