Samsung GU50TU8079U bad panel diagnosis

[Diah]

Re: Samsung GU50TU8079U bad panel diagnosis

right now it is sitting face down on my desk on blanket, yes. But of course I lifted it up to check the screen :P

I dont know what has caused this but the behavior now is different from what it started with.
1. When I got the set it rebooted after 2-10 minutes
2. after playing with tape and giving up it stayed on for hours with good picture except for 2-3 tiny lines
3. after a couple days it suddenly turned off and restarted immediately
4. playing with tape again I was able to keep it turned on but there were lines all over the panel (had to tape ~5 pins)
5. now taping all 14 pins is not enough to keep it from rebooting and the sound cuts off after a minute.

I am one step from cominng to the obvious conclusion that this tv is haunted

this point generally quids us first to check PSU and then Main boards...

[Ierwin]

Re: Samsung GU50TU8079U bad panel diagnosis

at that point I disconnected the mainboard and the backlight stayed on. Then connected the mainboard, disconnected ribon that leads to the panel board. Set stayed on. Then started taping until the set stayed on.
Whats strange is that none of this behavior has been constant.

inbetween it was perfecly fine without any tape and it ran for a couple days

[Diah]

Re: Samsung GU50TU8079U bad panel diagnosis

at that point I disconnected the mainboard and the backlight stayed on. Then connected the mainboard, disconnected ribon that leads to the panel board. Set stayed on. Then started taping until the set stayed on.
Whats strange is that none of this behavior has been constant.

inbetween it was perfecly fine without any tape and it ran for a couple days

don't panic... go back to the first points.. each place you did before tape mask clean the surface of the cable pins and seat hem correct .. also inspect if you did damage to the pins at any cause. .. all test you do just keep one U ribbon disconnected not ( yours new call C ribbon LOL )

[Davi.p]

Re: Samsung GU50TU8079U bad panel diagnosis

we have issue on main boards
its sound to me panel esd got defect short then mb suffer at dc dc converter...

this can't happen because every dc-dc or ac-dc converter from plain west to far east of the globe has many protection controls, short circuit especially..
lost for lost in the last attempts you can try remove the single TVS diodes on the panel boards, and check, single diodes test can't be made due to size etc.. but if you are lucky you can replace them with equivalent ones lately.. i guess clock lines to gate cog are not sensed for sh.cir. but VGL/VGH lines yes, so since protection takes place most of the times, you must concentrate to those 2 lines, plus VSS, another possible try that you can make is to locate by DMM in volt those caps on the mainb. and panel boards that levels the VGH/VGL and replace them, a possible leakage can there be..

[Ierwin]

Re: Samsung GU50TU8079U bad panel diagnosis

don't panic... go back to the first points.. each place you did before tape mask clean the surface of the cable pins and seat hem correct .. also inspect if you did damage to the pins at any cause. .. all test you do just keep one U ribbon disconnected not ( yours new call C ribbon LOL )

You are right, "U" describes it much better, lol.
I cleaned everything carefully and checke for bends.
Could not find anything unusual.

With the U ribbon connected the set still restarts before a picture comes on (backlight turning off and on again).

With the ribbon disconnected the program comes up and the sound is playing. Sometimes after a minute the sound cuts off, sometimes it runs for ages.
(I have been listeining to old baywatch episodes for hours, my brain hurts :P)

After the sound cuts off the set can still be turned off using the remote control. when I try to switch a channel on the remote, the red LED ligths up once but the sound does not come back.

For now I would preferr to ignore the sound cutoff, since it is hard to tell what is really causing it when I cant see anything. Afterall it might be network related because the programm it is set to is the samsung streaming service.

lost for lost in the last attempts you can try remove the single TVS diodes on the panel boards, and check, single diodes test can't be made due to size etc.. but if you are lucky you can replace them with equivalent ones lately.. i guess clock lines to gate cog are not sensed for sh.cir. but VGL/VGH lines yes, so since protection takes place most of the times, you must concentrate to those 2 lines, plus VSS, another possible try that you can make is to locate by DMM in volt those caps on the mainb. and panel boards that levels the VGH/VGL and replace them, a possible leakage can there be..

I really appreciate the ideas, but I have a hard time understanding what exaclty you suggest there. Removing parts should be the last thing to try and i dont know if I am at that stage yet. How can I test VGL/VGH?

[Ierwin]

Re: Samsung GU50TU8079U bad panel diagnosis

I read a bit about VGH and how it often causes Panel problems.
The VGH Testpoint on the left Panel board reads 0v when the U- ribbon is disconnected.
When I start the tv with the Ribbon connected the meter shows a voltage very briefly but the tv restarts before I get a reading.
If I had the schematics of the board I could check where the VGH comes from. Sice I don't have anything I might have to trace ist myself