SOLVED: A2337 820-02016 loose screw shorted PPBUS_AON Stuck at 5V

[it-solve]

Came not turning on. 5V 0A

When I opened it a screw came off from Q5800 area. There is a small spark indication on C5844


PPBUS_AON measures 135Ohm. Compared to 2.5MOhm on a spare board.

Cant detect any shorts or under 100Ohm spots, apart than PPBUS_AON. For a moment I got 5V 0.33A with Q5800 getting hot, but not anymore. Stuck at 5V 0A

Where do I start from? taking Q5800 and checking if resistance goes up on PPBUS_AON

 

[2informaticos]

You should compare diode mode readings between Q5800/20/40.
If no big difference, then try injecting voltage into PPBUS_AON.
I hope you really checked all secondary coils first.

Anyway, start with 1V and slowly increase; check with IR camera.

 

[it-solve]

I went through all coils, only AON lines are low resistance.

L5800/20/40 measures 0.193 instead of 0.367 on a spare board
Q5820/40 measurements align with spare board. only Q5800 is on the low side.

 

[it-solve]

It end up being a partially failed C5844, which seem to have happened after the screw shorted it. Lukicly didn't blow the CPU. A close one.