820-3476 - No Backlight at all

[pws6074]

Hi Guys,
No water or whatever liquid and board looks pretty clean, however, no backlight

Here is some measurements:

J8300
Pin 1 = 0
Pin 3-4 = 5
Pin 6-7 = 3.4V
Pin 28 and 30 = 5V

F7700 = 12V

U7700
Pin 5-8 = 5V
Pin 17-18= 0V


R7744 - 5V
C7744 = 5V

Q7700
3-4 = 12V


L7720
1 = 5
2 = 0

C7720
1 = 5V

D7720
1 = 5V
2 = 5V

Any hint ?

 

[2informaticos]

"L7720
1 = 5
2 = 0
---------
D7720
1 = 5V
2 = 5V"
That is impossible!
There is keyboard backlight circuit, but now I'm not sure if you didn't make an error on LCD backlight circuit too.
Please provide accurate information...

Recheck U7700 voltage, at least pin 18.
Do you get image for sure, just missing backlight?
Any USB activity?

 

[pws6074]

U7700
Pin 5-8 = 5V
Pin 17 0V
Pin 18 5V

Chime and Mouse OK

 

[2informaticos]

"Do you get image for sure, just missing backlight?"
???

 

[pws6074]

I can see the question mark, however, i don't have the back light.

 

[pws6074]

I figure out. The problem was C7715 ( short )
Everything works with the backlight. However, won't hold the battery.
Looks like is charging, but when i pull the charger the computer shut down
I did the hardware test (D) and NO ISSUES.

Lost again!

 

[2informaticos]

OSX recognizes the battery?
Does it show percentage, or some "Replace now" message?