New Project VIZIO D55-2 No Backlights..

[Michale32086]

Interesting story behind this...

It started out with a frazzled display panel that seemed to fix itself.. When you switched INPUTS, it would give you a green/black/grey jiggly lined frazzled screen.

This was 3-4 weeks ago.. After fiddling with it (IE turning it on and off, trying various inputs etc etc) it settled down and worked fine..

Gave it to a friend who used it for 3-4 weeks and it was fine.. He gave it back to me last Fri and said it wouldn't come on at all. A quick check confirmed that..

Started playing with it yesterday. It came on, the backlights came on and the VIZIO logo was clearly visible.. But I couldn't get anything on the display after that.. After a couple times at that, backlights wouldn't come on at all anymore, but I got a latent image of the VIZIO logo and that's it.. Still couldn't get anything to display past that...

Not really wanting to, but at a loss to attribute it to anything else, I broke the unit down to the bare LEDS.. as I suspected, the LEDS were fine. I checked the LEDs where the power comes in and each input (2 per connection) had between 16v and 16.6v which strikes me as a little low..

I am thinking to check the power PCB, but am unsure where to start..

Any assistance would be most appreciated. And I used to live on Whidbey, so...... (Family joke.. )

[Andrew F. Ali]

Re: New Project VIZIO D55-2 No Backlights..

Sounds like a Main Bd. issue...Perhaps a software update might help.

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

Sounds like a Main Bd. issue...Perhaps a software update might help.

Hmmmm Did not think about that.. Lemme try that..

[dick_barton]

Re: New Project VIZIO D55-2 No Backlights..

There appears to be 14 leds per strip so at 3V I would expect a minimum of 42V per strip. On each strip is the L+L connected together? Also the R-R?

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

There appears to be 14 leds per strip so at 3V I would expect a minimum of 42V per strip. On each strip is the L+L connected together? Also the R-R?

I am not sure what you mean?

The strips are in two sections...

[dick_barton]

Re: New Project VIZIO D55-2 No Backlights..

My thinking is since there are 4 wires per strip, are the two wires on the L's connected together. And also the same for the two R's.

It could be that if they are not connected together then they drive half a strip each so would be 7 leds at 3V = 21V rather than the 14 leds = 42V assuming they are 3V leds.

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

Sounds like a Main Bd. issue...Perhaps a software update might help.

I am trying a FIRMWARE update by inserting a USB via the VIZIO docs... The ThumbDrive is blinking steadly and sharply.. Not fading out like it sometimes does..

Been that way for about 10 mins now.. Not sure if I should assume it's not working or if it's just taking a while..
\

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

My thinking is since there are 4 wires per strip, are the two wires on the L's connected together. And also the same for the two R's.

It could be that if they are not connected together then they drive half a strip each so would be 7 leds at 3V = 21V rather than the 14 leds = 42V assuming they are 3V leds.

Gonna check this as soon as I get the USB/FIRMWARE UPDATE done... ish.

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

OK I just pulled it.. 20 mins was enough..

As far as the backlights, I did notice that there are no Ls on the second half of the strip...

Which makes sense.. I think.

Ya gotta remember, I am a duct-tape and superglue kinda tech..

[dick_barton]

Re: New Project VIZIO D55-2 No Backlights..

It looks as though the two L's drive the left half of the strip and the two R's the right half of the strip.

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

It looks as though the two L's drive the left half of the strip and the two R's the right half of the strip.

So, is 16V enough for that?? I wouldn't think so...

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

That would lead me to believe that it's the Power PCB that is the issue..

This is re-enforced by the fact I don't get any voltage on the marked connector..

On the other hand I have had instances where there was no voltages on the Power PCB because of a fault in the Main board...

[dick_barton]

Re: New Project VIZIO D55-2 No Backlights..

Where do all the 20V leads go to. Above picture.?

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

Where do all the 20V leads go to. Above picture.?

See pic..

I put a different but similar Power PCB on.. On the connector where I got 0v, I now get 24V.. But it still doesn't power the LEDs..

[dick_barton]

Re: New Project VIZIO D55-2 No Backlights..

So the 20V supply goes to the mainboard which has the led drivers built into it. Is that correct?

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

So the 20V supply goes to the mainboard which has the led drivers built into it. Is that correct?

Yea, that's what it looks like....

[Andrew F. Ali]

Re: New Project VIZIO D55-2 No Backlights..

Try disconnecting CN202 from the Main Bd. and see if it comes up if it does it means either the LED Drivers on the Main Bd. is not working or the LED backlights are failed causing the LED Drivers to go in protect mode.

[Michale32086]

Re: New Project VIZIO D55-2 No Backlights..

Try disconnecting CN202 from the Main Bd. and see if it comes up if it does it means either the LED Drivers on the Main Bd. is not working or the LED backlights are failed causing the LED Drivers to go in protect mode.

The only CN202 I could find was on the Power PCB.. I pulled it and still got the same result.. No backlights..

[dick_barton]

Re: New Project VIZIO D55-2 No Backlights..

Do you have all the voltages on the large white connector, PS_ON, ACD, 5VSB, 12V etc

[Andrew F. Ali]

Re: New Project VIZIO D55-2 No Backlights..

The only CN202 I could find was on the Power PCB.. I pulled it and still got the same result.. No backlights..

Pulling the CN202 on the PSU to disconnect it from the main Bd. was not intended to see if you would get backlights. It was intended for you to measure the pins to see if the 20Vdc came up. With the TV off disconnect CN202 then power on the TV and measure the voltage.