XBR55X850B Backlight, audio but no video

[BoardHoarder]

Trying to save a 55X850B from being scrapped but had no history of what was tried with this TV. Started off with no standby light but standby voltage present to main board and optical port would light up when plugged in, no tcon 12V or trigger and no BL ON. Bought used main on eBay and now have backlight, audio and the ability to turn set on and off from keypad and remote but zero video. 12V to tcon is good along with fuse, some DC voltages present on top side of tcon near LVDS cables but nothing on lower half but not sure what test points to use. How can I rule out bad panel or tcon? TIA

[nomoresonys]

Re: XBR55X850B Backlight, audio but no video

Test connector from mainboard to powerboard on powerboard side with all boards hooked up, test with tv plugged in but off then hit power, report both conditions here, give pin number, pin description/name and condition both off and when you hit power on. Procedure in second link below in signature if needed. meter set at 20 vdc.

[budm]

Re: XBR55X850B Backlight, audio but no video

Please post good clear straight shot of the whole T-CON board. There should be lots of Voltage test points on that T-CON board and we also need to check the DC resistance on those test points also.

[Duranitron]

Re: XBR55X850B Backlight, audio but no video

is the panel ok? you have backlight right? so look for obvious cracks on lcd panel. can you provide pictures for us to speed up the repair process.

[BoardHoarder]

Re: XBR55X850B Backlight, audio but no video

I can see that the panel is not cracked but I am more worried about shorted components on the driver boards attached to the bottom of the panel.

[BoardHoarder]

Re: XBR55X850B Backlight, audio but no video

Tcon

[budm]

Re: XBR55X850B Backlight, audio but no video

Pictures is not clear enough for me to read all the test points.
I can see VDD_L, VDD_R, VGL_L, VGL_R, VCC33.
Look for VGL_L, VGL_R.
You get the idea what we are looking for, Vxxx.
Test them Voltages
P/n of the IC next to the inductor with 220 printed on top?.

[BoardHoarder]

Re: XBR55X850B Backlight, audio but no video

I stared at the board and found every tiny round gold point and here’s what I get:
VDD_L 16.26VDC
VDD_R 16.28VDC
VGG_L -5.44VDC
VGL_R -5.44VDC
VCC33 3.34VDC
VCC18 2.01VDC
VGH_I_R 28.8VDC
VGH_I_L 28.9VDC
The top of that square IC that is symmetrical to the other side is TPS65162

[budm]

Re: XBR55X850B Backlight, audio but no video

Those Voltages look to be normal.
TPS65162 LCD BIAS IC.
https://cdn.badcaps-static.com/pdfs/...f85ec7ae25.pdf

[nomoresonys]

Re: XBR55X850B Backlight, audio but no video

Being a sony, they always recommend a firmware update after a mainboard switch, can you try it thru a flash drive?

[BoardHoarder]

Re: XBR55X850B Backlight, audio but no video

Is it possible to not have video from the main board or do those test points confirm that it is processing video? Any way to force a test pattern sequence?

[BoardHoarder]

Re: XBR55X850B Backlight, audio but no video

So purely by accident I do get solid colors to display on the entire panel. I put the USB stick with the firmware on it and did the factory reset with VOL- and POWER while plugging in. The standby light turned solid blue. I was checking connections on the main board and pulled the larger of the 2 LVDS cables and the screen went solid green, then red, then white and finally black. It just repeated this sequence until I reseated the LVDS and now back to a black screen with backlight.

[BoardHoarder]

Re: XBR55X850B Backlight, audio but no video

Looking into the LVDS cables at the main board paid off! They didn't appear to be evenly seated and the smaller one of the two was pushed in slightly farther and the little tabs at the end of the cable were torn off from not pushing the releases on top of the main board connection. Pulled out slightly on the LVDS and now have full and perfect video. Another 4K saved from the scrap heap. Thanks all for the help!

[budm]

Re: XBR55X850B Backlight, audio but no video

Good news, sometime good inspection helps, so it may have happened when you install the replacement main board.

[Marty-Club]

Re: XBR55X850B Backlight, audio but no video

Hi
do you have any advice how to remove a sony 65inch pannel to replace the back light strips.....