Similar to another LG UK series here
https://www.badcaps.net/forum/showthread.php?t=93943
Have backlight and sound. no LCD image.
Looks like bad T-Con section and perhaps RT6950. My question is
https://www.badcaps.net/forum/showthread.php?t=93943
Have backlight and sound. no LCD image.
- main board has integrated T-Con
- main board T-Con has LCD DCDC/PMIC RT6950GQW QFN68 package. Richtek chip. Can't find datasheet. Chip generates VADD (10.44V), VGH (~28V), VGL (~-14.5V)
- RT6950 pin 18-19 (clockwise) appeared to be bridged. Unlikely from my probing, looks like ball squeezage so it probably got hot
- Cleaned up bridging. Pin 17 is VGL (-14V) Pin 20 is VGH (28V). Pin 18 (I think 19 too) jumps between VGL and VGH voltage endlessly. Probably should be either VGH or VGL so likely chip failed.
- Disconnect right (looking at TV from front) panel driver board flex will get black image on left 1/2 and white image on right 1/2. VADD/VGH voltages looks good
- Connect right panel driver board flex (and the left) VGH and VADD all gets pull down to 1-1.5V.
- right and left panel driver board not symmetrical. Right board seem to be master (or have more signals) For example, 3.3V only supplied on right board and not left from main/tcon board (checked the left board's 3.3 signal trace. left board 3.3V dead ends after entering main+tcon from flex.
- Tested all caps on panel edge board. No shorts (all > Ks OHM on power rail side). Injected 1.5V 1A into AVDD and VGH rail, no current consumption, no FLIR hotspots.
- Voltage inject between different main rectangular ground pads on the edge boards only shows tiny current consumption. Shows full 1A consumption of +- injected on the same pad of course (as a reference to confirm properly injecting voltage) These ground pads are probably connected by panel matrix? So providing more confidence no panel matrix / COF tab shorts?
- All 6 drive chip on flex appears to not have burn marks (can only easily see the side towards the panel edge driver board. Other 1/2 hidden behind bezel which I didn't remove)
Looks like bad T-Con section and perhaps RT6950. My question is
- Anyone has datasheet for RT6950?
- Reasonable to conclude RT6950 pin 18 alternating between VGH and VGL is incorrect?
- What are the chances my panel + edge driver board failed? Seems like no short offers some confidence its good? But right edge board pulling down VGH and VADD is concerning. Of course if RT6950 is bad, then could just be that. I guess cost a main+tcon board purchase to find out if panel is good. haha.
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