820-00923 - 20v but dead

[Palhano]

Very strange board.

Mac arrived dead, but always with 20v. I disassembled it all to check, when I tested it, it worked. The board is perfect. I built the Mac, tested it for 2 days, now it stops working again.

When I don't work on the board for a few minutes and the charger connector, from 20v, pulls 0.7a and goes to zero.

PP3V3_G3H - 3.4V
PPBUS_G3H - 13V
PP5V5_S5 - 5V
PP3V3_S5 - 3.3V
SMC_RESET_L - 3.3V
RTC_RESET_L - 3V

any light?

 

[2informaticos]

Any fault history?
May have accumulated crap underneath some BGA chip.

PPBUS-G3H still has 13V when problem appears?
When works, battery is charging?

 

[Palhano]

No problem history. The Mac worked perfectly.

The PPBus always has 13v, even dead.
Battery charged normally during the two days of testing.

 

[2informaticos]

Do you get 3V3_SUS?

Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L (at same time).
If catch it, then check for pulse at big coils.

 

[Palhano]

Board resolved to work again. Waiting to see if it stops, to do the tests you asked for.