820-00928 No video

Similar to my other recent post except no video internal or external. No image or backlight.
This was a fully working MacBook that had a cracked display. Customer brought into a local shop that replaced the display resulting in this. Caps lights up, fans spin, in-line meter appears to show the Mac is on.
Disp connector on board/display side board and cable all look good (no charring on 43 & 1). Difference with this one is PP3v3/ PP5V_S0SW_LCD are at 0v.

Went ahead and replaced u8950 with some change in values but no change in function. Values before and after are below.

1) EDP_AUXCH_C_N - 0.693 > 0.469
3) EDP_AUXCH_C_P - 0.693 > 0.464
7) EDP_INT_ML_N<0> - 0.420 > 0.378
9) EDP_INT_ML_P<0> - 0.418 > 0.379
13) EDP_INT_ML_N<1> - 0.418 > 0.379
15) EDP_INT_ML_P<1> - 0.417 > 0.379
19) EDP_INT_ML_N<2> - 0.422 > 0.380
21) EDP_INT_ML_P<2 - 0.416 > 0.378
25) EDP_INT_ML_N<3> 0.416 > 0.380
27) EDP_INT_ML_P<3> - 0.416 > 0.380
4) BUF_EDP_PANEL_PWR_EN - 0.726 > 0.718
 
I do not get any pulse on PP3v3/ PP5V_S0SW_LCD with display connected or without. I do get PP3v3/ PP5V_S5 on u8500/01 and other S0 rails.

Does this point to u8500/01/10 for creation of S0SW_LCD?
 

2informaticos

Administrator
Staff member
PCH should first (temporary) enable power for LCD and waits DP_INT_HPD confirmation from it.
PCH has no firmware, but requires clean ME BIOS after changed is done.
 
Top