Sharp Aquos LC-42D43U

[mngopher22]

I have a 42 inch Sharp LC-42D43U tv that is exhibiting some issues with producing images. I did my research here on badcaps before posting. I believe i have identified the issue on the T-CON board. The 14 channel gamma buffer chip is bad and needs to be replaced. I came to this conclusion by measuring all the input and output voltages to this circuit.
The inputs to the circuit were
1 12.95
2 10.29
3 9.56
4 8.87
5 8.53
6 7.48
7 7.28
8 6.43
9 6.22
10 4.93
11 4.51
12 3.76
13 2.96
14 0.006

and the outputs of the circuit were

GM1 12.93
GM2 10.27
GM3 13.84
GM4 1.56
GM5 13.7
GM6 11.8osc
GM7 7.39
GM8 13.84
GM9 12.92
GM10 11.89
GM11 4.29
GM12 13.84
GM13 3.08
GM14 13.84

VGH 21.5
VGL -5.7
VDD 3.32
VREF 12.95
VGHP 23.78
VDA 13.85

The GM6 is actually moving around quite a bit. I didn't have a oscilloscope on hand to look at it but it should be a DC value.
I have included a picture of the TV operating and I am sure it is a bad gamma chip on the T-CON board but I am worried about the two white vertical bars on the right side. Are those white bars typical of a bad gamma buffer or is that more indicative of another issue?

[budm]

Re: Sharp Aquos LC-42D43U

Your GAMMA Reference Voltages are all over the place, and the way the image looks, yes, you do have bad T-CON due to bad GAMMA IC U6: AS-15.

[mngopher22]

Re: Sharp Aquos LC-42D43U

Your GAMMA Reference Voltages are all over the place, and the way the image looks, yes, you do have bad T-CON due to bad GAMMA IC U6: AS-15.

How about the white bars on the right though? Are the white bars a indicator of bad tabs or driver ICs?

[budm]

Re: Sharp Aquos LC-42D43U

The bars are not caused by T-CON board, you can try flexing the panel to see what happen to the board. it can be bad tab boding or bad connections on the ribbon cable between the LCD panel and the T-CON.

[mngopher22]

Re: Sharp Aquos LC-42D43U

I replaced the AS15 chip. I tested the voltages on the board before I put the TCON board back into the TV and all the voltages were now correct. I powered the TCON with a current limited power supply at 5 Volts. It only takes approximately 30mA at 5 volts. So the gamma buffer circuit now works and all the colors on the TV are correct. You can see the image below and see that the picture colors are now correct but I am still left with two vertical bars on the right hand side.

Next i tried pushing on the ribbons from the panel to the board but no luck. So next question is what should I try? Can i take a look at the signals to this board ? more specifically BR0 BR1 BG0 BG1 BB0 BB1 BCLK? I have a oscilloscope, I could check these signals and make sure they are at least valid. Anything else that I should check?