Macbook Pro A2338 820-02020 3V3_S2 missing

[Instafixx]

PPBUS at 12V.
Corossion near UC710 and UP7101.
PP3v3_s2 is 0.4V - No shorts.
PPBUS_AON_3VS2_VIN_ISNS is 12V
P3V3S2EN is 1.8V

i Replaced UC710. Now PP3v3S2 is 0V.
Others remain the same.

 

[2informaticos]

Check all feedback resistors RC709-13.
Be sure to have good solders and traces.

 

[Instafixx]

Resistance Across Pins

RC709 is 15 Ohms
RC710 is 0.8 Ohms
RC711 is 2.2 kOhms
RC712 is 35 kOhms
RC713 is 27 kOhms.

Traces look fine.

 

[2informaticos]

High value resistors can't be properly checked onboard.
Move them a bit, letting one pin free; this way makes the test easy.

"Traces look fine"
Tested in buzzer mode (until UC710)?

You can test removing CC719/20; possibly corroded.

 

[Instafixx]

Checked the resistors. the readings are okay with one leg removed - match with the schematics.
RC712 is 126 kOhms.

Removed CC719/20.

Still the same readings

 

[Instafixx]

When everything is connected. the fan goes max instantly and then reboots after sometime. macbook detects on AC2 with a padlock sign.

Tried DFU Revive. Stuck at Installing Software Midway with Fan spin at max. Then eventually it got cancelled automatically.

Now it is stuck at 5V. No Fan Spin. Not detecting in AC2.
PPBUS pulsing from 11 to 12.3v every 2 seconds

 

[2informaticos]

You've said UC710 gets power and enable; it should generate 3V3_S2.
Just in case, replace CC714; also try another UC710.

Did you check XWC711 too?

 

[Instafixx]

CC714 Voltage was pulsing. . Replaced. It is stable now.
Still no 3v3_s2. Should i tru DFU revive or replace UC710 again?

 

[2informaticos]

If UC710 gets enable, it should work...