[SOLVED]820-00165 No Backlight

[dam1inc]

water damage in the area of J8300, connector had blown pins 3 and 4, replaced connector and components around it. still no power to Pin 3/4
i have 8.6V to pin 1 of F7700, C7712 is .0V

 

[JohnB8812]

Did you check if the fuse is blown? Diode mode on backlight output?

 

[larossmann]

What voltage is on L7701, pin 1 and 2?

What voltage is on D7701, pin 1 and 2?

 

[2informaticos]

Is there even image?
Do you get USB activity, or chime?
Assuming yes, or at least DP_INT_HPD is high, post voltages at Q7700.
Check continuity to R5490.
Corroded XW7720 is common failure on Airs...

 

[dam1inc]

What voltage is on L7701, pin 1 and 2?

What voltage is on D7701, pin 1 and 2?

L7701 pin 1 .06v and pin 2 .20V
D7701 Pin 1 .20v and pin 2 .15v

 

[dam1inc]

Is there even image?
Do you get USB activity, or chime?
Assuming yes, or at least DP_INT_HPD is high, post voltages at Q7700.
Check continuity to R5490.
Corroded XW7720 is common failure on Airs...

i have faint image, USB works and i get chime
Q7700 all pins less than .10v
R5490 is blank
and XW7720 is corroded but i think there is a problem before this (but i did run jumper and tested continuity to pin 5 of U7701)

 

[2informaticos]

Sorry, my mistake; it should be Q7706, instead of Q7700...
As no voltage at L7701, check F7700 and post Q7706/07 voltages.

 

[dam1inc]

Sorry, my mistake; it should be Q7706, instead of Q7700...
As no voltage at L7701, check F7700 and post Q7706/07 voltages.

no worries, thank you for helping.
Q7706
pin 1 .01v
pin 2 3.3v
pin 3 .02v
pin 4 .01v
pin 5 3.3v
pin 6 .01v

F7700 pin 1 8.6v and pin 2 .01v

 

[2informaticos]

"F7700 pin 1 8.6v and pin 2 .01v"
F7700 blown, change it...

Be sure no short on backlight area, before power up the board.

 

[dam1inc]

"F7700 pin 1 8.6v and pin 2 .01v"
F770 blown, change it...

Be sure no short on backlight area, before power up the board.

ok thank you

 

[2informaticos]

To correct: F7700...

 

[dam1inc]

Replaced filter and problem solved thank you