820-00840 no image/Backlight


Hi, got this board, looks clean no signs of liquid.

no image, no backlight

external Display shows image

have connected a tested new display, with another mainboard, same flexcable image and backlight is ok.

tested already this things:

DP_INT_HPD pulse to 3.3V
BKLT_EN_R 0V no pulse
connector (44) PP3V3_S0SW_LCD pulse to 3.3V
connector (45) PP5V_S0SW_LCD pulse to 5V
PP5V_S0_LCD is 5V
BUF_EDP_PANEL_PWR_EN pulse to 3.3V

just now no idea anymore, need some help please
Last edited:


there is all 0V

Checked on the caps C8520-C8529 on CPU side and found out that C8529 pin 1 (EDP_AUXCH_C_N) has OL all the others have aound .212
I have the another same board with the same problem and checked this and same, C8529 CPU side OL
The "good" board has on all caps the same value in diode mode

seems like a common problem or i have the luck that i have 2 boards with the same issue :)

is it worth to try a cpu reflow in this case?