Vizio 32" SV320XVT Screen Black

[shredward]

My SV320XVT screen started flickering, intermittent at first and then slowly got worse until it was unwatchable. I did some research and figured it was the backlight inverter.

I opened the TV up, and while measuring the output on pin 13 of CN4 on the power board, I, er, kinda let the probe from my multimeter touch the live heatsink just below it and POP - GFCI tripped and now no backlight or picture.

I got the new inverter today and installed, and naturally that didn't fix anything due to the short.

Picture of the power board is attached
Unit can be switched from standby to on (vizio lights up from yellow to white)
No visibly damaged components
Fuse F1 reads 0 ohms while tv power is disconnected

Now, despite my being a total dumbass:
1. is there a way to isolate the problem on the power board I have?
2. should I just pop for a new board?
3. Did I just totally fry the TV and should just go ahead and part it out?

Thanks very much in advance.

[kevinm34232]

Re: Vizio 32" SV320XVT Screen Black

FYI had a SV370XVT, turned on but if I remember would not shut back off. Initially showed a partial Vizio logo on screen but then just blank. Was a bad main board, again..

[Mr Bill]

Re: Vizio 32" SV320XVT Screen Black

Have you checked all the fuses on the main board and tcon?

[shredward]

Re: Vizio 32" SV320XVT Screen Black

Thanks Mr. Bill...I didn't see those little fuses. They did all check out at 0 ohms.

Kevinm34232 - is there anyway to isolate the problem to one of the boards in particular?

[kevinm34232]

Re: Vizio 32" SV320XVT Screen Black

So what happens now, the vizio logo goes to white, but you have no sound or video? Are you able to shut the tv on and off?

[ben7]

Re: Vizio 32" SV320XVT Screen Black

Looks like there are voltage markings next to the connectors. It would be helpful if you could get a picture or two of those - good enough so we can see the markings/numbers!

First thing check, for standby voltage.

Check for craters or holes in any of the semiconductors on the PSU board.

[shredward]

Re: Vizio 32" SV320XVT Screen Black

On closer inspection of the PSU board I found a burnt trace coming from pin I shorted. I soldered a jumper wire to reconnect the trace, but it didn't change the problem: the tv will turn on and off (vizio logo goes white) but no video.

Attached are pictures of the voltage markings next to the CN3 (from PSU to main board) and CN2 (unused, same as CN4 that connects to backlight inverter).

Here are the measurements from CN3:

Pin 1 (PSON) - .058V when off, 3.27V when on
Pins 2,3,4 (12V) - 11.89V on all three
Pins 5,6,7,8 (SGND) - 0V and 0 ohms to ground
Pins 9,10,11 (5VSB) - 5.19V on all three
Pin 12 (A) - .063V
Pin 13 (B) - .003V
Pin 14 (C) - 3.25V

No external signs of damage to any PSU components.

Thanks!

[shredward]

Re: Vizio 32" SV320XVT Screen Black

Sorry, here are the pictures...

[shredward]

Re: Vizio 32" SV320XVT Screen Black

Also of note, if you apply 3V to CN3 pin 13 (B), the backlight illuminates...

[ben7]

Re: Vizio 32" SV320XVT Screen Black

Also of note, if you apply 3V to CN3 pin 13 (B), the backlight illuminates...

Good job! You tested the backlights all by yourself!

So, it is either a problem on a different voltage rail on the PSU, or a problem with either the t-con or the mainboard.

[shredward]

Re: Vizio 32" SV320XVT Screen Black

What would you recommend that I do next?

[shredward]

Re: Vizio 32" SV320XVT Screen Black

I just ordered a new mainboard from shopjimmy.com, so we'll see how this plays out when it arrives...

[shredward]

Re: Vizio 32" SV320XVT Screen Black

Ok, I'm back and still have a problem with the SV320XVT.

I have thus replaced, in this order:
Backlight inverter (original problem)
Main board
T-con
PSU board
Mainboard (again)
T-con (again)

When I power on the TV now, I get the Vizio image correctly displayed on the screen, with backlight on, but then the backlight turns off and won't come back on when watching tv or video. Audio and LCD is working working when I check with a flashlight, just no backlight.

This thing is basically a new tv...what do I check now?

Thanks in advance for your help.

[selldoor]

Re: Vizio 32" SV320XVT Screen Black

Does the backlight still come on when you jumper as in post 9

[shredward]

Re: Vizio 32" SV320XVT Screen Black

I haven't mustered the courage to take it apart for the 50th time yet, but the backlight does come on when it first powers up, then goes black after the visio logo appears.

[shredward]

Re: Vizio 32" SV320XVT Screen Black

Ok, so I put the original (bad) backlight inverter board in to troubleshoot, and presto...problem fixed, including the original backlight flicker that started this fiasco in the first place!

Thanks to everyone that helped...till next time!

Ed

[supermg]

Re: Vizio 32" SV320XVT Screen Black

hi, my vizio sv329xvt has the same problem as sherward's no video , no sound and the backlight turns on when the tv is powered on for about 30 seconds and goes off, the tv remains on but no picture and no sound, the power supply board is the same as posted by sherward.