Vizio VT420M speckled picture

[cat farmer]

Hello all,
So my Vizio has a very odd looking picture, one that I can't even find while searching the web. The image starts of jittery for 5 -10 minutes then settles down, but there is red and green shading on the image. I have replaced the tcon board, to no avail. I checked the LVSD cables and they seem to have continuity. I'm guessing it is something with the main board, but not even sure what to look at. I can do the component repair if I knew which ones to even look at.


thanks for any advice.

[budm]

Re: Vizio VT420M speckled picture

Solarized pictures, I am suspecting bad Gamma voltage, https://www.badcaps.net/forum/showth...ng+LN37A550P3F
Can you post the pictures of the T-CON board?

[cat farmer]

Re: Vizio VT420M speckled picture

Here you go...thanks

[budm]

Re: Vizio VT420M speckled picture

Picture is out of focus, I cannot read the p/n of the board. Is the IC as marked AS15?
Try re-seating the two cables on the bottom edge of the board.

[cat farmer]

Re: Vizio VT420M speckled picture

Here is a better picture. I have already replaced the tcon board, video is the same.

[mmartell]

Re: Vizio VT420M speckled picture

I think bud is implying you have replaced a bad tcon with another bad tcon.

I don't see AS15 on the chip - is this a variant ?

[budm]

Re: Vizio VT420M speckled picture

I look at shopjimmy picture: http://www.shopjimmy.com/media/catal...-1502b-top.jpg
It does not have AS15, I hope Tom will chime in and tell the OP how to test and report the Gamma voltage readings.

[cat farmer]

Re: Vizio VT420M speckled picture

Thanks guys. I found the service manual but it was worthless. Was more uesr manual then service manual. What happened to the good old days when a service manual told you how to fix a problem?

[cat farmer]

Re: Vizio VT420M speckled picture

So I noticed the service manual I downloaded is missing pages 37 thru 63 which are the pages I need. Found that version a few times on the web. Anyone have the complete manual?

[tom66]

Re: Vizio VT420M speckled picture

I don't think this is a gamma fault, it's not even across the image. I think it's more likely you have a loose LVDS connector, contaminated connection, or bad/misconfigured main board.
If you want to test gamma voltages, they are probably on the points near the ribbons marked V17,V16,V15,etc. down to V1.

[tw2005]

Re: Vizio VT420M speckled picture

can you get into the service menu with this? Press "Menu" and then press the following combination: "1," "9," "9," "1"

[cat farmer]

Re: Vizio VT420M speckled picture

can you get into the service menu with this? Press "Menu" and then press the following combination: "1," "9," "9," "1"

yep, been through the service menu. I reset everything with no change. I ran burn in and the colors all looked good. I am going to look at the LVSD cables again today, see what or if there is something wrong with them, but without a schematic or voltage reference I'm just guessing. I did find that unplugging the right cable made almost no difference to the picture, but by looking at the cables the left one may be the one that carries the voltage to the T-Con, as it has more connecters on it.
my search continues..
Thanks for the help

[cat farmer]

Re: Vizio VT420M speckled picture

Ok now i did something really stupid., I set the LCD to the wrong type in the service menu and now I have no picture. Anyway to recover from that?