Vizio E470VL backlight circuit sensitivity

[Taterbug]

I have been working on an Vizio E470VL for months and it is driving me crazy that I can't fix it. I plays for just a few minutes (5 at the most) then the back light shuts down. Every time I loose the lamp voltage going to the PS board. I have replace the power supply board and also have replaced the main board THREE times and still having the same problem. Last night I went as far as to tear the whole thing down and remove the LCD screen and examined the Backlight lamps and associated wiring looking for arc spots. I did find one small spot next to the connector on the circuit board that holds the lamps. I cleaned that spot and insulated it thinking it would cure the problem. The spot was very very small about the size of a pin head. I reassembled everything and still have the problem. I found a new set of cables on e-bay that I ordered. This is about the only thing left that has not been replaced. I ohmed out the lamps to gound using a VOM on megohm range and could find no shorts to ground. Is their anyway to make the Lamp feedback circuit less sensitive? Or do you think it could possible be a bad cable? I should get the cables in a couple of days and that will eliminate that problem. I have also just installed a new eprom on the new main board I received just to double eliminate that problem. Anyone else had this problem???

[Caleb]

Re: Vizio E470VL backlight circuit sensitivity

Is the inverter on the power supply? Can we see some pictures? It sounds like you may have one or more cfls that are taking more amperage than the inverter likes then it shuts them off. Shopjimmy shows about 4 different power boards used in this model. Which does your tv have? If it will turn on with the screen removed you can check for dim bulbs, or ones with black stripes around the end.

Sometimes it is just better to move on for a bit and come back to it later. Ive got a Samsung that wont keep the backlights on for more than a few seconds, waiting for another cracked screen to come in with compatible bulbs as I cant get enough matching tubes to make the balancer happy.

[stj]

Re: Vizio E470VL backlight circuit sensitivity

what do the tubes look like?

if they are ice-white with silver ends they are new,
if they are white with darkened ends they are old,
if they look a bit yellow and the coating looks powdery instead of smooth they are done.

[budm]

Re: Vizio E470VL backlight circuit sensitivity

"I ohmed out the lamps to gound using a VOM on megohm range and could find no shorts to ground" The meter cannot put out 2000V to simulate the high voltage than can cause high voltage break down.
I agree that you may have bad lamps, or still arcing some where.

[Taterbug]

Re: Vizio E470VL backlight circuit sensitivity

The bulbs look white and it has a beautiful picture when I can get it to play. I tore it back down and double checked for more arc spots and did not see any. If the cables that I've got coming don't fix it then I will just hold on too it until I can find one with a cracked screen. Thanks.

[stj]

Re: Vizio E470VL backlight circuit sensitivity

how many tubes does it use?
is it edge-lit or back-lit?

[Taterbug]

Re: Vizio E470VL backlight circuit sensitivity

Here is a photo of the backlights...

[budm]

Re: Vizio E470VL backlight circuit sensitivity

So when you turn it on right now, you do see ALL the lamps light up, right?
BTW, which version of this model do you have? The one with power supply-inverter combo board? Or the one with separate power supply, inverter board.
LCD panel model number?

[stj]

Re: Vizio E470VL backlight circuit sensitivity

10 tubes - damn that's gotta generate some heat!

[pongagt]

Re: Vizio E470VL backlight circuit sensitivity

10 tubes - damn that's gotta generate some heat!

There are 20 tubes and my VO420E has 18 tubes.

[Taterbug]

Re: Vizio E470VL backlight circuit sensitivity

All the lamps DO light up. I have the model that has the PS and inverter board combined. I have replaced this board as well as the main board ( twice ). I did find some arc spots underneath the boards that the lamps are connected too. I cleaned these areas and reinsulated with electrical tape. Still same problem!! Waiting on cables to arrive but this really has me stumped. Plays at most two or three minutes before I loose lamp signal shutting down back lights. ?????

[audiofreak19]

Re: Vizio E470VL backlight circuit sensitivity

Do all of the ccfl bulbs light up to the same brightness. If one is duller then the others it means its on the way out. That could be the only thing I would think since you have replaced the main and power board multiple times. Does your model have the t con built into the screen or is it a separate board? If it's separate or I guess even fixed if for some reason there is a fault in the t con and it shuts down and looses the video signal it will shut the backlights off.

[audiofreak19]

Re: Vizio E470VL backlight circuit sensitivity

When the tv backlight turns off can you still shine a light behind it and still see a picture. That would eliminate the t con and panel.

[stj]

Re: Vizio E470VL backlight circuit sensitivity

There are 20 tubes and my VO420E has 18 tubes.

i know it looks like 20,
i assumed it was using "U" shaped tubes or it would need twice as many invertor outputs.

[budm]

Re: Vizio E470VL backlight circuit sensitivity

Are there any small blue caps on the board where the lamps are connected to?

[budm]

Re: Vizio E470VL backlight circuit sensitivity

OH, and the LCD panel model number?

[Taterbug]

Re: Vizio E470VL backlight circuit sensitivity

All the lamps light equal. Tcon combined with main and no caps on boards. Should have new cables by Tuesday. If that don't fix it then I will set it aside until I find one with a broken screen and use for parts.

[Taterbug]

Re: Vizio E470VL backlight circuit sensitivity

I took off the LCD screen and the White plastic cover where I could observe all of the lamps real close. I found the problem one of the lamps was starting to flicker just slightly and could only be noticed with the white plastic screen removed. I removed the lamp and that solved the problem of the backlight shutting down. Now to find a replacement lamp. Does anyone know a source where I can buy a single lamp? I would replace all of them but have already spent a ton on this set. I am planning on just replacing the single lamp for now and keep the TV and watch it a while to make sure everything is ok.

[audiofreak19]

Re: Vizio E470VL backlight circuit sensitivity

Ccflwarehouse.com

[Taterbug]

Re: Vizio E470VL backlight circuit sensitivity

Thanks