Macbook A2338 PPBUS Cycling

[Instafixx]

PPBUS cycling - No Shorts.
Stuck at 5v. 0.45 Amps
3v3_s2
3v8_aon
All diode mode readings are okay but voltage is fluctuating.

Upon thermal imaging. I found RN420/21/22/23 getting very hot when connecting the board to charger.

No Shorts on these. Resistance across Pins are 9.8Ohms.

PP2v5_AWAKE_NAND has 3.4V.
PP2v5_NAND0_Discharge has 0.4V

 

[2informaticos]

Any history available?

3.4V on 2V5 NAND power rail is really bad.
Check if R770C is good.
If is, then probably bad U7700.

P2V5_NAND0_DISCHARGE_EN should be high once PP2V5_AWAKE_NAND is disabled.
In fact, QN420 should discharge the remanent voltage on this power rail.

 

[Instafixx]

R770c across pins is 3Ohms.

P2V5_NAND0_DISCHARGE_EN is 1.5V now.

Replaced U7700.
Now pulling 20V.

PPBUS stuck at 12V

 

[2informaticos]

Try DFU now...