Samsung UE50f5000AW, backlight ok, no image no osd

[yoritomo]

Hello all

This TV is lighting on the the backlight, but the screen still be black, no OSD or images appears, I checked the power supply , all voltages are OK.

T-con model is AUO T500HVN05.0

I guess the problem is coming from the T-con, any one can inform me how to diagnose it with the test points on it ?
I can fix and check gamma problems already but this one is different,and information about t-con are always painful to find. I made a tour already of the smd fuses and diodes, but no results, surely a chip.
Some test points should display on oscilloscope the digital video signal .

Thank you for your help

[yoritomo]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

I have some new informations , i made a test disconnecting the ribbons on the t-con on pannel side, surprisingly i got a perfect half image disconnecting right one. doing reverse give a blank screen.
i noticed something strange on that side on the corner, i didn't mind yet until now cause i found no relations, but the lower left corner has a damage, a small cloud of dead pixels always on, and a kind of small burn on the plastic.
Then i checked the the rule circuit soldered to pannel, no trace of liquids, burns or any, capacitors and fuses looks good.

I start to feel like the panel itself is dead.

[budm]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

Are you getting 12VDC between the chassis GND and each end of the SMD fuse on the T-CON board?

[yoritomo]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

It depends which fuse exactly because i have only one really close do the lvds connector, this one is 12.76V, the other , I could find another one close to a small AUO chip which has the same value. no change if I disconnect the panel ribbon.

[budm]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

So you do have Voltage feeding the board.
Good clear pictures of the T-CON board will help so we can see what we are dealing with.
Also try having ribbon cable between the T-CON and the panel connected one at a time to see what happen.

[yoritomo]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

This is a clear picture i could find on the net, better than mine .

As i said already above i already unplugged alternatively the ribbons and could get an correct half image on right side.

[budm]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

This is a clear picture i could find on the net, better than mine .

As i said already above i already unplugged alternatively the ribbons and could get an correct half image on right side.

Sorry I missed post 2 about the ribbon cable, at this point the problem is in the LCD panel. It can be due to shorted Gate/Source drive ICs on the flexible PCB between the LCD glass panel and the tab bonding board, or shorted parts such as MLCC on the tab bonding board.

[yoritomo]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

I reversed already both ribbons to check them but no luck, on the PCB pasted to the panel I see a small 8 pins IC, that may be the bad one, but I don't know how to test it, it is the only component I still doubt there.

[budm]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

There should be lots of light tan color rectangular caps (MLCC) that usually shorted out of have high leakage resistance,

[victor_cj]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

You need to indentify and isolate with a litlle piece of duct tape only de VGH signal from the ribbon with problem.

[yoritomo]

Re: Samsung UE50f5000AW, backlight ok, no image no osd

On this model needs to disassemble all the shield, one surely burnt inside, that is the reason the plastic melted, thank you for your help . Now I understand what happens on it.