820-00923 no backlight

[Kyle93]

Arrived with no liquid damage. Works fine with external. Already tried new screen.

Replaced U8400 and Q8400. Surrounding components are good.

Only 0.45V at BKLT_EN_R

Where to go from here? No shorts found

 

[Kyle93]

Yes there is internal image on screen just no backlight

 

[2informaticos]

Check diode mode to ground at both pins of D8410; w/ and w/o screen connected.
EDP_BKLT_EN missing too, no pulse in the first seconds?
Be sure R8442 is good.

 

[Kyle93]

d8410 pin 1 0.792 pin 2 1.105 with screen pin 1 0.792 pin 2 1.098

EDP_BKLT_EN missing. pulse of 0.80V in the first seconds

R8442 is good

 

[2informaticos]

The new screen is known good working?
EDP_BKLT_EN comes from PCH.
If you get image, LCD is detected and PCH should enable backlight.

 

[Kyle93]

Solved. Bad lcd cable even though it looked good

 

[2informaticos]

Do you mean the short cable, between MLB and screen lid?

 

[Kyle93]

yes

 

[2informaticos]

Good to know, never faced with this problem.
Thanks for feedback.