Troubleshooting • Finding the cause of no USB power

Hi, I accidentally got caught out with a couple of spots of rain with an uncovered Pi 3B (not plus) streaming from a camera. Whoops. Now all USB (including wifi and ethernet) is completely dead. Zero volts on the USB ports and PP27 (viewtopic.php?p=628505#p628505). Obviously I've blown something up... any thoughts would be very much appreciated.

It boots to the desktop fine and it sounds a lot like the symptoms here, including the very short flash of USB power when powering on:
viewtopic.php?p=1774175

So I wondered if I should attampt to replace the LAN9514 chip.

But, I'm also getting a continuous overcurrent warning after the rainbow boot screen, with power supplies I know to be good. Also the green LED doesn't light up at all.

Would it still make sense that it's probably the LAN9514 that's been damaged?

I thought the AP2553 (U13) is what chooses to trigger the overcurrent warning with its fault pin and I did try the idea of removing it here:
https://awsh.org/raspberry-pi-repair-no ... r-message/ and here: viewtopic.php?p=1115444#p1115444

But that changed nothing. It does look like it works together with the LAN9514. Maybe both could be bad or maybe some other unknown thing is wrong too?

- The fuse is ok
- 5V and 3.3V are ok and PP3 to PP1, 2, 8, and 9 are nowhere near shorted
- U13 didn't get hot once the Pi was damaged

Statistics: Posted by andy29 — Tue Jul 08, 2025 4:14 am

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