LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

[maneatingmonkey]

Any idea what could be causing the left half of the screen to be completely black and the right half completely white?

No picture from any input or OSD. The audio, however, works fine. Also, the backlight changes intensity along with the input feed.

I've tested the voltages on all the marked test points I could find and everything reads OK.

I've tried applying both heat and pressure to the tabs connecting the panel to the buffer boards to no effect.

Unplugging the white ribbon cables going into the 2 buffer boards on the black half of the screen has no effect. Unplugging a ribbon cables going into a buffer boards on the white portion of the screen turns that quarter black.

[nomoresonys]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

Do you have about 12 volts on each side of the tcon fuse? black - probe on chassis ground red + probe on each side of fuse.

[maneatingmonkey]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

Do you have about 12 volts on each side of the tcon fuse? black - probe on chassis ground red + probe on each side of fuse.

Yep, FP1 is continuous and measures 12V on both sides. The other test points labelled V__ measure fine too.

[nomoresonys]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

Maybe check the MLCC caps on the buffer boards, see if any of them read very low ohms.

[maneatingmonkey]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

I did some more probing and of the buffer boards and found that VDDA on the right two boards (white half) was 17.7V, while VDDA on the left two boards (black half) was 0V. I traced VDDA back to VAAR (right side) and VAAL (left side) on the T-Con board, and confirmed that VAAL was shorted to ground! I discovered a couple surface-mounted capacitors were to blame.

Unfortunately, I can only find replacement V500DK1-CKS1 T-Con boards from overseas, which with shipping are all more than I'm willing to spend. Plus, I inadvertently damaged the contacts on one of the ribbon cables while testing Oh well, at least I've isolated the problem and know that the other boards are all OK to sell.

[diif]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

Why not just replace the capacitors and damaged cable ?

[nomoresonys]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

Seems like a nice 4k tv, I think you already did the hard work, ie figuring out the fault, nice work, I would try replacing those bad caps and find a replacement ribbon.

[maneatingmonkey]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

What value caps would I even replace them with?

[diif]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

What value caps would I even replace them with?

Measure the working ones on VAAR.

[maneatingmonkey]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

I don't have anything to measure capacitance with :|

[maneatingmonkey]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

So now that the short is gone, when I connect the right two buffer boards I now get an image on that half of the screen (instead of solid white). But when I connect the left two buffer boards instead, I now get vertical bars and no picture (instead of solid black).

I actually put back one of the SMD caps, since only the second one I removed was shorted, even though both were in parallel, and it didn't change anything. So I suspect that there is another fault either on the T-Con board, or somewhere in the buffer boards or panel themselves?

[viewerau]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

Any update?

[RooTV]

Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A

Hi
I know its a long shot but you didnt happen to open this up and get the part number of the LED's?
I have this tv and am looking at getting replacement LED's but only want to open it up once.
Cheers