820-2915 no green light

[Yoel Ren]

hi, this board doesnt work on original magsafe 85w adaptor, but when i plugged fake chinese magsafe, it can turn green one second, and then its gone, with fake chinese charger, R6990 start smoking

with original magsafe, i don detect any voltage at all, no ppbus, no pp3v42 , no ppdcin and chrgr_dcin_D_r ( measured at d7005 )

 

[2informaticos]

Fake charger doesn't have embedded processor and is not able to detect leakage or any other short on the machine.
It will always deliver full voltage; that's the reason some boards get burnt!

Looks like you have a problem with C/U6990
Check diode mode (red probe at ground) AT C6990 and L6995.
Which is the actual value (onboard ohm scale) of R6990?

 

[Yoel Ren]

diode mode of L6995 is 0.319 on both side, compared to another board, same value
c6990 is not shorted but diode mode is 0.08, changed to new one, 0.4, board now have a green light and can turn on after 2 cycle of fan spin, i don think this is normal
it can detect battery percentage, but if magsafe is unplugged, it instantly shut down.

 

[Yoel Ren]

ppbus with battery : 11.39v
ppbus without battery only magsafe : 8.56
resistance 27/28 u7000 : 21 ohm
resistance 17/18 : originally 0.0 something ohm, so i changed the r7052 and r7051, now 2.9 ohm
i have changed u7000 too

 

[2informaticos]

Probably bad D6990.
Do you get 3V42 on battery only?

 

[Yoel Ren]

I don get pp3v42 without battery, d6990 pin 2 and 3 is shorted, replaced and problem solved, thanks a lot 2informaticos!