Grundig 55 GUB 8860 - bad T-Con or bad panel?

[Ierwin]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

use cool spray or heat MB see which part will make the tv displaying good picture in case no BGA at main IC

Okay so I just gave the cooling spray a try. I disconnected the left ribbon cable so I got a good picture on the right side. As said before this fades to gray after a few seconds.
By cooling the MB I was able to get the picture to come back.
This seems to work best right after the TV is plugged in, so I found it dificult to tell what area of the MB reacts to the cooling.
I attached a picture of the MB and the area that gets the picture back when cooled. Spraying directly on IC300 didnt help, it more in the area left of it.

Since I have the black screen when both cables are connected and also the MB changing with temp, could it be that both T-con and MB are broken? That would be really bad luck.

[Ierwin]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

I would be checking t-con voltages with ribbons unhooked and connected. You could also check and see if your lvds signals are still there.

Could you explain which Testpoints I should be checking?
I did some searching yesterday and found the t-con fairly cheap online. Would be definetly worth to repair the set of it turns out that only the tcon is bad.

[dskall]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

I would be checking t-con voltages with ribbons unhooked and connected. You could also check and see if your lvds signals are still there.

[Diah]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

When I connect the other cable to the tcon the connected half of the panel stays black while the disconnected side goes white.

first my memory it seem going bad, yours tv with external t-CON so---
yours panel are fine don't play with it at all. either your T-CON, you have drooped signal feed with main IC on main boards. reason could be BGA or caps on MB. use cool spray or heat MB see which part will make the tv displaying good picture in case no BGA at main IC
BTW- if you have at the panel boards at the middle U ribbon try disconnect one and see the result.

[Ierwin]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

So I did some reading and came across other threads of people having the same or quite similar issues.
One suggestion is always to check the capacitors on the driver board of the faulty side for shorts, which I did but could not find any.
Another apparently common fix is to tape certain parts of the t-con connector. One video I found specifically mentioned blocking the CLOCK signals.
I attached a picture of the T-Con.
The left side of the board where the ribbon cable is disconnected in the picture is the one that corresponds to the faulty side. Powering up with the cable disconnected like in the attached picture gives me half the image as shown before.
Unfortunately only the right connector has pins that are clearly marked CLK1 to CLK10, so I have no Idea where to start taping.
I randomly taped pins on the left cable but could never get anything but either the completely black screen (same as with fully connected cable) or the half white, half working (as it is when the left cable is disconnected)

could the fact that even with the left cable disconnected the half picture does not stay stable but instead fades to grey after a few seconds indicate that the T-Con ist faulty too? Like maybe the faulty panel has killed the T-con, therefore taping does not help?

[Ierwin]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

so its a panel issue?
Anything worth checking or is thin generally an unrepairable thing?

[dskall]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

In this case I might suspect the side with the picture is dragging down voltages.

[Ierwin]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

What does other side do?

When I connect the other cable to the tcon the connected half of the panel stays black while the disconnected side goes white.

[Diah]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

GUB 8860 as much i remember it had T-CON interrogated at panel, can you show here the back side..

[dskall]

Re: Grundig 55 GUB 8860 - bad T-Con or bad panel?

What does other side do?

[Ierwin]

Hello everyone,

so another broken LCD found its way on my workbench and I take the opportunity to dig into analyzis and learn something in the progress.

Unfortunately I could not find a service manal for this device, but at the moment I am not even sure that schematics would be much help.

When I power up the set the screen stays dark. I can see that the backlight lights up but there is no picture on the screen.
I suspect that this is either an issue with the t-con or with the panel itself.
To rule out one or the other I detached the cables of leading from the t-con to the panel one by one. With the left cable removed I get half a picture for a short time, before it turns into just some gray lines.
I attached pictures that show the individual stages of startup.

With the right cable removed and only the left connected one side stays white, the other black.

I read that when you get half a picture with one cable removed it is likely that the disconnected side of the panel is bad. However I am not sure if this is the case here because the other side does only hold the picture for a couple of seconds.
Is it worth hunting down a replacement T-con?
Anything else I could test to narrow down the root cause?

Best regards

Kolja