Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

[DXseekerMO]

Hello everyone,

So from the free pile I picked up a Samsung UN55MU6290FXZA.

Symptoms and observations:

Power Supply voltages at correct values

Plug the TV in, turns on by itself, continuously attempts to re-boot itself, control by remote/buttons on back of the TV is lost.

Horizontal lines emanate from the left side of screen on first boot attempt.

The COFs from the screen to the source driver boards do not appear to be overheated or damaged

Diagnostic actions and observations:

Detaching one LVDS cable from the screen at the Main Board upon either the left or right side results in continuous re-boot stopping and restoration of user control by remote.

There are no apparent shorts of any components on the source driver boards, but a few components on the right board, inboard side have suspicious low Vf (voltage forward) readings of .180

With both LVDS cables attached voltage test points (VDD, VA, VSS) have some voltage upon them just before the backlights illuminate then voltage drops off or disappears altogether shortly after.

This looks like a screen fault of some sort. The question is, can this be repaired or worked around with a side tab removal or similar action? If not, does anyone have any specific diagnostic routines I can apply to narrow down the problem?

[neilc6]

Re: Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

These newer models without tcons are more difficult to diagnose and not sure if the left/right side test applies. I had one that didn't turn on and then the owner told me later the screen was hit on the far right side. I ripped the tab bond off in that section and the TV turned on. Can only check the power supply and backlights are good by disconnecting the main/ps cable.

[DXseekerMO]

Re: Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

These newer models without tcons are more difficult to diagnose and not sure if the left/right side test applies. I had one that didn't turn on and then the owner told me later the screen was hit on the far right side. I ripped the tab bond off in that section and the TV turned on. Can only check the power supply and backlights are good by disconnecting the main/ps cable.

My guess is since user control is restored by disconnecting one LVDS and the "continuous re-boot" stops indicates a screen fault. So this model does have side drive tabs?

[DXseekerMO]

Re: Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

There are no side drive tabs upon the screen, and there is no damage to the side of the screen.

[alfatv]

Re: Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

You can try scotch tape method. Don't ask me which pins, just try different locations.

[DXseekerMO]

Re: Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

You can try scotch tape method. Don't ask me which pins, just try different locations.

I never thought of that....but for some reason I had it in my mind that doesn't work on TVs without a T-con? I will try though!

[alfatv]

Re: Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

I never thought of that....but for some reason I had it in my mind that doesn't work on TVs without a T-con? I will try though!

Those are the cables after T-con, so it doesn't matter if T-con is standalone or integrated into MB.

[DXseekerMO]

Re: Samsung UN55MU6290FXZA, backlight flash, user inputs null, screen malfunction

Those are the cables after T-con, so it doesn't matter if T-con is standalone or integrated into MB.

So the strange factor goes up. If I cover up one trace the TV still constantly tries to re-start, however if I cover up 2 traces it doesn't.

After that I tried covering only the 2 outboard traces, 2 at a time on each side of both LVDS cables and the TV does not try to re-start. It also responds to the remote but still no picture.

This is so strange!