Vizio SV420XVT Distorted Picture Issue

[Timebomb606]

Hey guys,

I got this TV from a friends parents who thought it was broken. When i got it home, i did a channel search and all was well. Well when i unhooked the coax from RF Input, the connector broke off and was on the end of the cable...no longer attached to the TV.

So i got a new main board for this and installed it all. Exact same serial, and product code as the old one. Turn the TV on and nothing at all, no backlight, no sound, no vizio logo light up...nothing.

So i have put the old board back in and im going to return the new one. Well now when i put the old one back in...its working fine, just the picture is all distorted as if something isnt connected right. All connections are fine as far as i can tell. There was a piece of "aluminum tape" id assume is what it is, prob for grounding purposes that isnt connected. It went from power supply board to chasis that covers the main board.

Can that cause problems? No blown caps i can see, nothing else was touched at all.



Any help would be appreciated.

[Timebomb606]

Re: Vizio SV420XVT Distorted Picture Issue

Anyone?

[Mrx3750]

Re: Vizio SV420XVT Distorted Picture Issue

Either the new board is defective, or has the wrong software (programmed for a different LCD panel) Not sure what on your old board would cause a distorted image, except possible programming issues. Can you post a pic of the distorted image?

[aaronwt6]

Re: Vizio SV420XVT Distorted Picture Issue

Pictures of the boards and whatever the TV is doing would be very helpful in getting you an accurate response. My first hunch though on the original board is that it is in working condition and that you have a tab bond issue on the screen resulting in a distorted picture. If you are getting a motion blur effect with ghosting of images then that's most likely the culprit. You probably were just lucky the first time and the tabs had reconnected briefly from moving it around.

[aaronwt6]

Re: Vizio SV420XVT Distorted Picture Issue

You may have also just not reseated a cable well or have a tcon issue. Here's an example of one I got with a tab bond problem.

https://www.badcaps.net/forum/showthread.php?t=28659

[Timebomb606]

Re: Vizio SV420XVT Distorted Picture Issue

I have nothing like those pictures.

Heres a few screenshots of the picture and the boards. There used to be a piece of tape from the yellow power supply to the cover over the main board. That wouldnt cause that image issue, right?

Thanks again for your replies so far.

[Mrx3750]

Re: Vizio SV420XVT Distorted Picture Issue

That is a strange one. You seem to have the correct colors, just the image rendering is off. I'm wondering if electro static discharge might be to blame? Maybe when you removed the old board, you just set it aside, or maybe even threw it in the trash? Then when you realized the new board was faulty, you rescued the old board.

I don't think missing grounding tape would cause such a weird issue.

[aaronwt6]

Re: Vizio SV420XVT Distorted Picture Issue

This is certainly something I haven't seen before. You'll have to wait for someone else to chime in on this.

[Timebomb606]

Re: Vizio SV420XVT Distorted Picture Issue

Alright, yeah when i removed the old board to install the new one. I just set the old one aside and then switched them back. Any idea if static discharge is an issue, is fixable?

[Mrx3750]

Re: Vizio SV420XVT Distorted Picture Issue

Electro static discharge can do all kinds of crazy things to motherboards, which is essentially what your chassis board is, a specialized motherboard. Things I've seen are a frozen BIOS clock, and yes, weird video errors. Not quite like yours, but you get the idea.

Now as to how fixable it is, easiest solution for you I think is to send your new board back for a replacement. I'd wait until someone more knowledgeable sees this thread, but it's likely not easily fixed.


Then again, if you could find the firmware and do a firmware update, who knows?

[Timebomb606]

Re: Vizio SV420XVT Distorted Picture Issue

Its just so frustrating that it was working perfectly fine. Didnt change anything and now its not working.

Doesnt seem like it anything related to power, both boards i have power on. New board doesnt show a picture, only backlight comes on, nothing else. Cant use the power button to turn off either. Have to unplug it.

Old board allows TV to be turned on, shows that messed up picture though.

[Timebomb606]

Re: Vizio SV420XVT Distorted Picture Issue

So does anyone have a picture/diagram of what voltages the LDO's would have on this TV?

[Timebomb606]

Re: Vizio SV420XVT Distorted Picture Issue

Anyone have any other ideas what to check to diagnose this issue?

[tom66]

Re: Vizio SV420XVT Distorted Picture Issue

The voltages are written on the regulator for example LM1117-33 or LM1117-18 indicate 3.3V and 1.8V respectively. Or, if it is not labelled, the output is not directly known, but you can check the regulator function: the voltage between pins 1 and 2 should be approx 1.25V (+/-0.05V)