Vizio VT420M No picture

[landyboy]

I picked up another one to try to fix. I give the ones I can to relatives. This one is a Vizio. I have test the power board and all the proper voltages 5v, 12v and 24v. The back light appears to come on as I can see a faint blue background and the vizio emblem lights up. Any suggestions? As you can see I improvised the fuse temporarily as it was missing when I opened the TV????

[tom66]

Re: Vizio VT420M No picture

From the rear of the chassis you should see light come through some holes when plugged in, do you?

[landyboy]

Re: Vizio VT420M No picture

Yes I do.

[tom66]

Re: Vizio VT420M No picture

The backlight is working, then. We will need a picture of the T-con board. Trace the leads going from the power supply. One will go to the top of the TV. This leads to the T-con board.

[landyboy]

Re: Vizio VT420M No picture

Here you go....

[landyboy]

Re: Vizio VT420M No picture

Both screws appear to be missing. Am I correct?

[tom66]

Re: Vizio VT420M No picture

It does look like that; is that how it came to you?

Here is the fuse on the T-con.

Check the voltage on both ends -- red probe on each end, black probe on chassis, tell us what readings you get.

[landyboy]

Re: Vizio VT420M No picture

No voltage either side.

[landyboy]

Re: Vizio VT420M No picture

Yes this is how it was when I opened it up. I guessing it may have been worked on before but I'm not sure.

[tom66]

Re: Vizio VT420M No picture

That was with the backlight on? No voltage either side means there's an issue on the main board.

[landyboy]

Re: Vizio VT420M No picture

Yes when powered up and turned on there is light in different areas. I have attached another pic.

[landyboy]

Re: Vizio VT420M No picture

I assume it is DC voltage that I am checking for correct?

[landyboy]

Re: Vizio VT420M No picture

I may have pulled a senior moment. Once powered up there is 11.38 volts each side.

[tom66]

Re: Vizio VT420M No picture

Either the main board is not sending a signal.
Or the T-con is defective.

It looks like T-con replacement has been attempted, so I would look at the main board.

Follow this guide:
https://www.badcaps.net/forum/showthread.php?t=22231

[landyboy]

Re: Vizio VT420M No picture

Any chance it could be a bad LCD panel?

[tom66]

Re: Vizio VT420M No picture

There is a chance, I suppose. We've found that to be very rare though.

[landyboy]

Re: Vizio VT420M No picture

Ok thank you I appreciate all your help, one last quick question. Is there any chance of repairing the main board?

[tom66]

Re: Vizio VT420M No picture

Probably -- did you see my post above re. voltage regulators?

[landyboy]

Re: Vizio VT420M No picture

I will take a look at that now. I did notice when reassembling the Tcon cover I noticed the two screws I thought were missing actually go through the cover and the board so I'm not sure they changed the Tcon Board.

[tom66]

Re: Vizio VT420M No picture

That would make sense. I would personally recommend a t-con board exchange first, if it has not been swapped before.