820-3332 strange problem :)

[Patricia]

Hi to all nice people

I have a very odd problem , on one 3332 board when I connect the charger I get a green light just for a sec and then off .
I connected it to the bench power supply to start measuring and the board magically turned on ???!!!
I put it back and connected everything and on the normal charger it does the same thing green for one sec then off ... connected it to the bench power supply and the computer works completely normally , boots and everything ... noticed a small lag in the mouse movements though .
Took it out again and it repeats the same thing , works on bench supply but not on 85w charger , needless to say I tried 3 different chargers and the result is always the same green for a sec and nothing .
Tried it with everything disconnected and replaced the dc in board still the same .

Do you have some advice ?
Thanks a lot in advance

 

[2informaticos]

Original (smart enough) Apple charger detects leakage on inpout circuit.
And it doesn't want to power up the board.
Usually caused by Q7080, or D6910.

Post exact value of R6912, measured onboard (ohm scale).

 

[Patricia]

Thank you 2informaticos
both the Q7080 and D6910 "look" nice , no corrosion .... the R6912 has 22 kOhms ...
Should I replace the Q7080 and D6910 ?

 

[2informaticos]

D6910 can be checked in diode mode.
I recommend you to change Q7080.
I never saw both of them bad at same time...

 

[Patricia]

Just one small odd thing before I replace the Q7080 , I just made some measurements before and I found something strange , the R7081 measures just fine 62 kOhm R7080 is 4k instead of 100k so I replaced that one with a proper 100k ....as soon as I soldered it on it was back on 4.3k grrrrr so I replaced it again and the second one was back on 4.3k.....
Can I take the q7080 from a donor board or should it be new ?

 

[2informaticos]

That is 100% sign of leakage on Q7080, change it; R7080 is OK, don't bother more with it.
You can pick it from scrap board, but check to have clean terminals.

 

[Patricia]

Thank you soooo much 2informaticos

as always you are right , after replacing the q7080 everything back to working normal .
One more time thanks a lot , much appreciated , you can mark this thread as solved .

best regards