Telefunken T37P884 FHD 100 DVB-T horizontal corruption

[BenTennyson]

This is a Telefunken T37p884 (Vestel chassis/boards) with LG panel.

PSU working with stable rails, TVset turns on but has horizontal lines/picture corruption.

Backlight inverter, PSU, Upscaler and TCon are good. (at least I presume that because I replaced the PSU, Upscaler and TCon boards with reviewed used ones from a spare part shop)

The corruptions cover the entire screen (the tvsets own menu display too) and so they obviously also occur on every signal source.

The upper few rows of pixels are always good.
These corruptions will vanish if I let it sit like that for a few minutes and it will then continue to display fine until I shut it down. Behavior is reproducable.

The board seems to desynch from the HDMI-signal for a second on rare occasions while it is in this "warmup phase".

I measured the power rails of the PSU under load directly on the mainboard, everything stable and meeting the specs to 100%. Voltages on the smaller two caps on the mobo fluctuate between 6-7volts. I dont know if that is ok, [s]cant find schematics for that board.[/s]

Already replaced the three caps on the board since they were bulged, but obviously they weren't the cause of this fault.

Would you say this might be an issue with the mainboard or maybe with the ribbon cables that go from the TCon to the display interface, like user ReeceyBurger123 suggested?

I uploaded a video of the fault to Youtube, so you can actually see whats goin on in motion:
https://www.youtube.com/watch?v=Mj9qVfbir1c

See attachments for further visual material. It includes the display interface, tcon, upscaler and top and bottom view of the mainboard. I also uploaded a hires version of the top view of the mainboard.
Please forgive my less than average manual stitching skills. (That picture is also zipped because of server restricions on JPG files).

I also found this service manual for the mainboard with schematics just before completing this posting, but unfortunately it is for revision 1, not 4.


Further device data:
Mainboard: Vestel 17MB35-4 060109

Display:
LC370WUD
(SB)(A1)
Factory ID: LGDWR
Serial 37099W6630660 681C
LG Poland

6900L-0261E 090913 QSU USD99D7WHSUQ0VSV0261EUNA0

inverter shield imprint: 3550S-0648A 201
inverter print: LG Display CO. Ltd. 66321-0543A 37SL-0(L) T1
PEOPLEWORKS CO,. Ltd. PPW-EE37SL-0(L) Rev1
L2-EF37-1-09504H-BJ L

Display-Interface:
LG Display Co. Ltd
P/N: 6870S-0679A (Source left) - 6870S-0680A (Source right)
DESC: LC370WUD-SBA1, LC370WUN-SBA1 SOURCE LEFT/RIGHT
Designed: 2008.09.06

[BenTennyson]

Re: Telefunken T37P884 FHD 100 DVB-T horizontal corruption

(Sorry for doublepost, editing isnt enabled)
Update:
I further took apart this abomination, got deep into its guts down to the fluorescent tubes of the backlight.
I connected everything with its guts taken apart.
Please note that this panel doesnt have tab bonds on the sides or bottom, only on top. I tried to mess with the bonds (pressing, wiggling etc) in the 'warmup-phase' with the fault visible. Didnt make any difference.
Then I waited till the fault went away and started to ice components.

I basically iced the whole mainboard, tcon and upscaler, but the corruption didnt come back (although it smelled funny and made crackling noises when the chips boiled the stuff away again).

I don't know what to do anymore except replacing the flex cables. Shelling out even more money just to see the fault stay. Maybe. This sucks.

[martino]

Re: Telefunken T37P884 FHD 100 DVB-T horizontal corruption

BGA chip fault came to mind right away.In this case that would mean upscaler board?
But I would think mainbord BGA chip fault,but it doesn't seem to have a BGA chip..
Ok,method I would use to determine what is giving you grief.
First off,I would spend a good bit of time cleaning the LVDS cable(mainboard/t-con board)with alcohol,cotton swaps etc. It's free to try and could be a real possibility for this fault.
If that fails,I would concentrate on the "warm-up" period you mention. I however,would use a hair dryer,not freezing.
I would start with a "cold" tv,where you would expect to see the fault with,but hair dryer the mainboard for a few minutes first,see the result.
Repeat method on t-con,upscaler board etcs,till you see a way shorter "warm-up" period.

Often,when a certain board fails,it's kinda a typical thing on that model,so buying guts from another tv is certainly not a proof that it's not those board,as in why did that tv get gutted?