A1278 820-3115-B no backlight

[hgoncalves]

Hi,

I have an A1278 820-3115-B with no backlight. It works, gives image on external monitor, and with a flashlight on the back, it shows image.
I don't understand this readings:

On F9700 I get 0V on the pad 1 and it seams that PPBUS_3GH is shorted
PPBUS_3GH = 0V 0 ohm and 0V on diode mode.

But everything seams to be working besides the backlight.

Already removed F9700 with same readings.

Can you help?

 

[2informaticos]

I hope you removed charger and battery when tested diode mode at F9700.
In fact, you should allow 15-20s before making any ohm, or diode mode reading on PPBUS_G3H.

Post D9701 voltages, if exist.
Be sure R0910 is good first.

 

[hgoncalves]

Hi,
D9701 has 0V on both sides, and R0910 seams to be ok 0hm.
PPBUS_SW_LCDBKLT_PWR_SW seams to be shorted (0V in diode mode). shall i replace U9701?

 

[2informaticos]

Lift L9701 (one pad) and check where the short remains.

 

[hgoncalves]

It's on PPBUS_SW_BKL
Already replaced C9712, C9713 and R0910 but still shorted

 

[2informaticos]

How can R0910 generate a short to ground???
Is strange that you didn't check which side of R0910 the short remains; once you've removed it.

C9712/13 are the suspects there.
If none shorted, then should be a short between copper layers.
Be sure the short is not on pad 2 of L9701...