A1278 820-2936-B backlight

[hgoncalves]

Hi,
I have an A1278 820-2936-B that has no backlight, and it's breaking all the F9700 fuses.
When I lift up the fuse, I don't see any short on the pads, but when I replace the fuse, it burns again.
Already tried with 2 LCDs.
What shall i do from here? Can you help?

 

[2informaticos]

Post diode mode to ground at both sides of D9701; w/ and w/o LCD connected.
Also check if Q9706 is not already shorted S-D.

 

[hgoncalves]

D9701:
W/O LCD:
1 = 0.450
2 = 0V shorted but diode looks good (only passes voltages from one direction).

Q9706 seams to be ok.

This is a 50V line. What voltage should I inject to figure out where the short is, or is there a better approuch?

 

[2informaticos]

Why to inject voltage?
There are only 4 caps and U9701.
Very likely the chip is bad.
Inspect LCD connector too, just in case.

However, for pure short, 1-2V should be sufficient to heat the culprit.

 

[hgoncalves]

Hi,
After replacing U9701, LCD connector, C9796, C9020, C9799, turn out to be C9797 . It gave a fight, but it turn out to be a success!
Thanks!

 

[2informaticos]

You should start removing the caps...