820-01521 No image on LCD but image on External Monitor OK

No-Clean

Member
Clean board boots fine, I get image on external monitor, tested with 2 known good LCD screens and new LCD flex, no image either. Tested in the Macbook case and just board and test screen, same results.

No shorts on LCD connector

SMC_LID Left and Right are both 1.6v
PANEL_P5V_EN 3.2v * Should this be 5v?
PP5V_S0SW_LCD 5v
PP3V3_S0SW_LCD 3.3v
U8510 pin 1 3.3v
 

2informaticos

Administrator
Staff member
"PANEL_P5V_EN 3.2v * Should this be 5v?"
Why would you expect 5V on enable signal?
Make difference between signals and power rails.

Check levels on pins 1, 2, 4 of U4802.
Also check DP_INT_HPD, if steady high.
Do you get any voltage at PPVOUT_S0_LCDBKLT?
 

No-Clean

Member
Thanks for the lesson.

Check levels on pins 1, 2, 4 of U4802:
All are around 0v, I replaced U4802 and now they are
SMC_LID_LEFT 1.6V
SMC_LID_RIGHT 1.6V
IPD_LID_OPEN 1.8V

DP_INT_HPD steady 3.2V

PPVOUT_S0_LCDBKLT 0V not shorted and correct diode measurement reading
 

No-Clean

Member
No history available, came from other shop.

Diode mode measurements for DP_INT lines of J8500.

DP_INT_HPD 0.560
DP_INT_AUXCH_C_N OL but R8503 is fine
DP_INT_AUXCH_C_P 0.260
DP_INT_ML_C_N<0> 0.270
DP_INT_ML_C_P<0> 0.270
DP_INT_ML_C_N<1> 0.270
DP_INT_ML_C_P<1> 0.270
DP_INT_ML_C_N<2> 0.270
DP_INT_ML_C_P<2> 0.270
DP_INT_ML_C_N<3> 0.270
DP_INT_ML_C_P<3> 0.270
 

2informaticos

Administrator
Staff member
Seems to have broken trace for DP_INT_AUXCH_C_N.
The diode mode to ground reading is decided internally into PCH.
 

No-Clean

Member
DP_INT_AUXCH_C_N is OL but R8503 pin 1 and J8500 pin 1do have connection, R8503 pin 2 (PP3V3_S0SW_LCD) diode reading is on par with another working board measures 0.490

T2 was already revived but no luck.
 
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