Vizio M401i-A3 backlight and sound but no picture

[serow]

I have gotten for free a Vizio M401i-A3 LFTGOZAP that has backlight and sound but no picture, solid black. I gather from skimming a few other threads that I should be looking at the TCON board. I don't have an oscilloscope and haven't had any luck finding a service manual; are there any tests I can do with a multimeter that would be useful?

The power supply capacitors look fine.

I've seen a very large thread on the e701i-A3, but this unit only has one LVDS cable from the motherboard to the TCON, so it's pretty different from the e701i-a3.

TCON is labelled: RUNTK 531TP 0075FP and 38A49 and ZZ
It seems to go for about $20 used/ebay/amazon and I've found a website selling for $40 condition unstated, but a 180 day warranty, is that typical?

I've done my share of repairing computers with replacement fan/heatsink assemblies, and specialized Dell parts, but I've never bought TV parts before.

[ecking767]

Re: Vizio M401i-A3 backlight and sound but no picture

Have you check the fuse with a multi-meter?

its label F100 Near the flat ribbon cable

[serow]

Re: Vizio M401i-A3 backlight and sound but no picture

F100 (the really flat one with "P") is continuous

[budm]

Re: Vizio M401i-A3 backlight and sound but no picture

Do you get 12V between GND and the T-CON fuse?

[budwich]

Re: Vizio M401i-A3 backlight and sound but no picture

even though there is only one lvds cable, that doesn't really matter. One of the tests / checks, is to unplug one of the tcon to panel cables and see what happens / changes. do the same, with the other and see if there is any difference, this might help point you in a certain direction... as a panel issue (and edge board) or the tcon itself.

[serow]

Re: Vizio M401i-A3 backlight and sound but no picture

Sorry for not replying earlier, the weekend kinda got away from me.

Do you get 12V between GND and the T-CON fuse?

I do.

even though there is only one lvds cable, that doesn't really matter. One of the tests / checks, is to unplug one of the tcon to panel cables and see what happens / changes. do the same, with the other and see if there is any difference, this might help point you in a certain direction... as a panel issue (and edge board) or the tcon itself.

Disconnecting the right-hand panel cable (seen from rear) results in no change, backlight no picture.
Disconnecting the left-hand panel cable (from rear) results in that side of the panel (right side from front) solid white, and the other works normally.

[budwich]

Re: Vizio M401i-A3 backlight and sound but no picture

thus it appears your problem is with the "left side" (from rear) as disconnecting the "fault condition" allows the tcon to function enough to create a picture... if I understand your observations. You probably need to provide pictures of the screen to "enforce" your "word observations" (to get those 1000 words) along with pictures of the board / back panel layout / connections especially near the panel.... ie. the lower edge boards where the tcon to panel cables connect. Based on your tests, it is a possibility that the edge board has a failed component (smd capacitor / resistor) that is causing the one side to "choke" the tcon preventing it from operating.... this may be considered a "panel failure" since the edge boards are not replaceable as they are bonded to the panel with tabs that can't replaced in the "field".

[serow]

Re: Vizio M401i-A3 backlight and sound but no picture

Oops, I already forgot this board allows picture attachments, even though I used them

Here's the relevant pictures.

I don't see any visible problem with the edge board, so the panel (and TV) is probably a write off then?

[budm]

Re: Vizio M401i-A3 backlight and sound but no picture

https://www.badcaps.net/forum/attach...5&d=1528249555
Look for shorted caps on the board that corresponding to the side of the panel that has no pictures.

[budwich]

Re: Vizio M401i-A3 backlight and sound but no picture

as budm suggested, you need to check the components BUT not with your eyes, use a meter. plenty of threads where people have found a bad smd on the edges of various sets and have been able to careful replace with the board attached to panel. having said that, it was free so your choice on wlhat you want to invest.