A1708 820-00840 No Backlight

[Djsp]

Hello solved the problem of Flexgate by replacing lcd, but it does not have backlight, here are some measurements:
PPVIN_S0SW_LCDBKLT_F = 13V
PPVIN_S0SW_LCDBKLT =12V
EDP_BKLT_EN= 0v
BUF_EDP_PANEL_PWR_EN= 3.40v
EDP_PANEL_PWR_EN= 3.10v
PANEL_P3V3_EN_DLY= 3.29v

 

[2informaticos]

"EDP_BKLT_EN= 0v"
Don't waste time checking backlight circuit, if is not even enabled!

Do you get image for sure?
3V3_S0SW_LCD both present?
What about DP_INT_HPD?

 

[Djsp]

I get both one and the other for a second then 0 I just get to imagine external

 

[2informaticos]

So DP_INT_HPD is not stable?
Then you don't have image.
Try known good LCD assembly.

 

[Djsp]

Could it be a bios problem? Lcd I tried it on in another car and it works

 

[2informaticos]

Check diode mode to ground on EDP_INT lines.

 

[Djsp]

EDP_ML_C_P 0.320
EDP_ML_C_N 0.319
EDP_ML_C_P 0.320
EDP_ML_C_N 0.320
EDP_ML_C_P 0.319
EDP_ML_C_N 0.321
EDP_ML_C_P 0.320
EDP_ML_C_N 0.320
EDP_AUXCH_C_P 0.320
EDP_AUXCH_C_N 0.320

EDP_INT_AUX_N OL
EDP_INT_AUX_P< OL
EDP_INT_ML_N <0> OL
EDP_INT_ML_P <0> OL
EDP_INT_ML_N <1> OL
EDP_INT_ML_P <1> OL
EDP_INT_ML_N <2> OL
EDP_INT_ML_P <2> OL
EDP_INT_ML_N <3> OL
EDP_INT_ML_P <3> OL
Previously I had focused on U8400 C5451/52 were short I replace them but nothing
the problem is with the image I think even if I get external video

 

[2informaticos]

Did you change small video cable too?

PCH expects high level on DP_INT_HPD; else no internal image at all.

 

[Djsp]

Do you mean on j8500?

 

[2informaticos]

Yes...