820-3332: No power, MagSafe light turns green and off, then repeats

[cobragfox]

Anyone experience this fail before, when the MagSafe is connected, it keeps flashing green and then goes off, then repeats. Does this over and over.
Once i go to test PPBUS_G3H the voltage starts to drop from about 11v and the MagSafe stops flashing, stays off. Same on PP18V5_DCIN_ISOL. When measured at F6905, i get about 15v just before it starts to drop, but it keeps repeating. I pulled Q6910 and confirmed PP18V5_DCIN_CONN had 16V on it. Any ideas?

 

[2informaticos]

Does it work with pre-charged battery?
Possibly leakage on the input MOSFET.
Post R7080/81 and R7085/86 values, measured on the board.

 

[cobragfox]

Looks like Q7080 may be the issue.
R7080 measures to 0.407K when it should be 100K
R7081 - 62K approx
R7085 - 472K approx
R7086 - 333K

And with battery connected, the spans spins for about a second and shutoff.
Going to pull Q7080

 

[cobragfox]

So magsafe has stopped blinking and acting like it should. New issue, the fan spins for about a second the shuts off, then repeats and keeps doing this.

PPBUS_G3H - 12.58v
PP18V5_DCIN_ISOL - 16.5v when the fan is off, and 20.5 once the fan kicks on before it shuts off again and goes back to 16.5v

 

[dukefawks]

Was this board messed with? Fans that do on/off is not a good sign

 

[cobragfox]

The guy said it was a faulty power supply, having the polarities reverse. Not sure how he would have done that unless if he was attempting to repair the MagSafe.