Failed Raspberry PI Repair
I recently found a Raspberry PI 4B in the trash and wanted to try to repair it.
Plugging it in, there were a couple hot-spots on the board and checking with a multimeter revealed that the 3.3v line was almost totally shorted to ground, with only 100ohms of resistance. Feeling the board when it was powered, both the VLI USB chip and the DA9090 power regulator got quite hot to the touch.
After removing both of those chips, however, the SoC gets quite warm. It's not hot enough for me to be sure there's still a short, but it seems likely given how these devices usually seem to fail. Unfortunately replacement DA9090 chips are not available; some hackers online have gotten the MXL7704 to work instead by running the I2C communication lines through an Arduino first to translate the Pi's request to the correct I2C address. Quite the process, when I'm already pretty sure that the SoC is toast, but maybe I'll come back to it at some point.
