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820-00923-A Internal display not working, Booting , But no chime sound

M

manumathew.017

Member
Working fine with an external monitor, Internal display is not detecting, Tried connecting another internal display but still no back light or image.
History - Coffee spilled
Found corrosion on display connector (Not on logic board but on display board). Cleaned it up , Still no change
 
2informaticos

2informaticos

Administrator
Staff member
Overvoltage went back to MLB through the video cable.
Compare diode mode to ground on the EDP_INT data lines.
 
M

manumathew.017

Member
EDP_INT_AUX_P - 0.216V
EDP_INT_ML_P<0> - 0.239V
EDP_INT_ML_N<0> - 0.239V
EDP_INT_ML_P<1> - 0.239V
EDP_INT_ML_N<1> - 0.239V
EDP_INT_ML_P<2> - 0.239V
EDP_INT_ML_N<2> - 0.239V
EDP_INT_ML_P<3> - 0.239V
EDP_INT_ML_N<3> - 0.239V
PPVOUT_S0_LCDBKLT - 1.120V
PP3V3_S0SW_LCD - 0.553V
PP5V_S0_ALSCAM_F - 0.441V
PP5V_S0SW_LCD - 0.550V

I found the one pin burned on the LCD connector(please find attachment), I don't have the schematic of the display board to figure out the net name.

A1706_lcdissue - Google Drive

drive.google.com drive.google.com
 
2informaticos

2informaticos

Administrator
Staff member
EDP_INT_AUX_P/N must give almost same reading for diode mode to ground.
If not, CPU's eDP output is burnt; there is no series cap to protect it.
 
M

manumathew.017

Member
It may be a stupid question...
Is there any workaround for this signal? By wiring it from any of the USBC display data signals? Or only solution is to change motherboard?
 
M

manumathew.017

Member
I can see similar signals on display mux page , For example DP_DDI2_ML_C_P<0> .....DP_DDI2_ML_C_N<3> ,DP_DDI2_AUXCH_C_P / N , Will it make sense routing it to internal display? ;)

Another question, Any idea about what activities take place by EDP_INT_AUX_P/N. If it is not dynamically driven we can pull them into a high or low?
Because I can see there is a provision for a pullup and pulldown resisters R8502/3

.
 
M

manumathew.017

Member
I agree,
Should I try feeding (display mux) inputs directly to display?
for example U3610.
If you say it's not possible sad let's close the issue here
 
2informaticos

2informaticos

Administrator
Staff member
I don't really understand what you want to do.
The eDP bus is bad; you can't get image on internal LCD anymore.

U3610 is dedicated for external DP, through Thunderbolt.
 
M

manumathew.017

Member
I mean , Can we replace the eDp bus with DP_DDI? What I understood DP_DDI is also display signals but not for internal display but for external. They multiplux and give for four USBC connectors. My question is , Can these signals drive internal display?
 
2informaticos

2informaticos

Administrator
Staff member
Backlight is controlled by PCH and will not work, once eDP is damaged.
Internal LCD image and backlight are related.
 
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