Sony KD-75XF9005 grey Picture but Sound. TCON or panel?

[iglitare]

Hi,

i want to repair a Sony KD-75XF9005 TV that initially only showed a grey picture.
Backlight seems to work, Sound (Setup menu after reset) works.
If i dissconnect the left FFC cable from TCON to panel i have half a screen on the right. If left cable is connected always only the grey screen.
Interchanged the cables, its always only the right side that is working. Always grey if left side is connected.
With my small knowledge i would think at least the cables are good.

Can this happen because of a bad tcon board?
Or is it always a bad/shorted panel?

[tiki66]

99% a bad/shorted panel. Do a tape fix

[Diah]

show please yours screen how it look

[Davi.p]

Hi, are you from Albany? The fault is probably a shorted capacitor on the panel strip board, left side, on the AVDD line (15v line).. check it first with ohm meter without power, i say to you the rest later..

[iglitare]

I can take pictures as soon as i am at my brothers house again (it´s his TV).
But it was just grey lit. With left cable from tcon to panel disconnected it was half ok, other half grey lit.

Hi, are you from Albany? The fault is probably a shorted capacitor on the panel strip board, left side, on the AVDD line (15v line).. check it first with ohm meter without power, i say to you the rest later..

Thanks for this info, i will check it! Unfortunatelly no, i am not from albany.

99% a bad/shorted panel. Do a tape fix

thats what i feared. I will try tape fix after i measured the cap Davi mentioned.

Before i try the tape fix, is there any way to determine what pin is shorted (measurements with multimeter or oscilloscope)? Or even blow up the short with overcurrent so that is just a open line?

And if i try the tape-fix, what lines should i tape?
I would guess the pins towards the center of the pcb where all the traces go to the big chip (left side pin 80 and lower)?

[Davi.p]

I thought so because of your nickname Igli Tare football player..

first i think you have bad cap, i'm convincted because otherwise you saw the half screen white not black, apart this if it would be the common fault with the tape "cure" , i feed doubts about the technique of the "short" killer, because i think the fault could not be a short in gate drivers, but a current deficit..

[iglitare]

I thought so because of your nickname Igli Tare football player..

Hillarious :-) but i am just an old fan of him since he played in a team i like

first i think you have bad cap, i'm convincted because otherwise you saw the half screen white not black

ok, that seems plausible, i will check in a few days if there is a shorted cap

apart this if it would be the common fault with the tape "cure" , i feed doubts about the technique of the "short" killer, because i think the fault could not be a short in gate drivers, but a current deficit..

Sorry, i tried to understand this sentence.
Do you mean taping does no work (reliably)?
Where are the gate drivers? directly on panel, unaccessible? Or on the small board of the Panel that holds the connectors to the tcon?
And where and why and what would be the current deficit?

[ivtv1]

These pins are always at the end of the tape.
https://www.youtube.com/shorts/3jD2pe_qUEE

[Davi.p]

No, i mean the Short Killer is not a good technique maybe, i'm suspecting... the tape trick at least preserve what is already good.. the gate drivers are on the vertical sides of screens, today are more common integrated to the glass, where previoisly was on small Cof tabs..

[iglitare]

It´s getting weired ;-)
I meassured no short at AVDD line.
So i tried the tape method.
I doubted the right pins were on the right outside of the right connector, since the lines are kind of thick and marked with V...
So i masked 12 lines that looked right:

Wow, it worked, full screen visible. (and AVDD ob both connectors now 15V, before only 15V on both when only left connector was connected and half screen was visible)
I then unmasked one after the other of the 12 lines, (off course turned off TV each time.).
Even after unmasking all lines Picture stayed full screen.
Wow. Put TV together, powercycled a view times, all good.
After half an hour exact error like before.
Full grey screen until i disconnect right cable from tcon to LCD, then half screen worked.

Was it a coincidence? Did i even masked the right CLK lines?

Can anyone take a guess where the CLK lines are? Shouldn´t it be 8 instead of 12?
Here another picture:

[lotas]

A common problem in Sony TVs is their LVDS cables and cables, sometimes cleaning their contacts or completely replacing them with new ones helps.

[Davi.p]

indeed i am curious about the ribbon connection.. but where to take a some good auality one?

[iglitare]

A common problem in Sony TVs is their LVDS cables and cables, sometimes cleaning their contacts or completely replacing them with new ones helps.

I guess not in my case, since disconnecting right cable tcon<->panel gets me a half working screen.
That's why I ruled Mainboard and LVDS out. Was that wrong?


Anyone an idea where on the picture the clk lines for taping are?

[Davi.p]

I wouln't be sure if would in you.. if you can gather a surely good ribbon.. we learn a new thing... :-)

[angelos]

Check my photo. I think there where i boxed it in red is where you need to play around.
Regards

[iglitare]

Check my photo. I think there where i boxed it in red is where you need to play around.
Regards

Thanks. That was the area I taped.
But as I said, after taping, picture looked OK, untaped the pins one by one an after unmasking all, picture stayed OK for half an hour. Then all grey again.
I think I try it again.

Strange thing was, even with these 12 lines taped picture looked not distorted, no lines, it looked perfect.
Can that be? I would have expected a bad looking picture when all lines are taped.

[angelos]

Sometimes those LVDS cables can mess around with a poor connection. try getting new one's andsee what happens.

[iglitare]

I can try to order some LVDS cable if i find a reliable source.
And then? Perhaps change the TCON board?

I really thought it would be definitely a panel related error, since half screen works after disconnecting right FFC Cable TCON-Panel.

[Davi.p]

Half a screen means half current in it, if the ribbon.can't handle the correct current?

[Diah]

I can try to order some LVDS cable if i find a reliable source.
And then? Perhaps change the TCON board?

I really thought it would be definitely a panel related error, since half screen works after disconnecting right FFC Cable TCON-Panel.

75 size huge one, corner of the panel could be damaged easily , you dont need to disconnect one ribbon of half screen.... you have on Panel buffer boards 2 U ribbon shape cable, disconnect one of time and see which side will display 3/4 panel size good image