820-02536 board Air 2022 A2681 with power cycling on USB

This 820-02536 presented with areas of liquid damage in the R_SPKRAMP area near UN000. I removed two corroded caps that had shorted PPBUS_AON and PP1V25_AWAKE_NAND to ground.

Now, connecting a charger gets PPBUS of 12.3V and 5.1 on USB-C. The charger gets to 20V but as soon as it does, the connection is reset to 5.1V and power cycles as such. Same behavior on all 3 ports.

I checked all large coils as well as the smaller MPMU and SPMU output coils and could not find shorts to ground. No component is getting hot during cycling. There’s obviously a short somewhere, how do I find it?

PPBUS_AON steady 12.3V?
What about 3V8_AON?

Also check MPMU and SPMU LDOs.

PPBUS and 3V8 are steady for a few seconds, until the power resets and all rails dip to zero. Need to check the LDOs.

All LDOs for both PMUs are there, some briefly, some steady.

Did you test with battery connected?

I did and nothing changed at all. The battery could be empty though. I need to verify on another A2681 machine.

Unfortunately I don't have a charged battery or a functional A2681. Anything else you would check?

Check diode mode on any switch, like in pages 48, 76, 78.

A good battery tester is a "must have" tool nowadays.
This is the cheapest and best option, especially designed for Apple repair.

Harald has also a battery simulator for some MacBook boards.