Today, I've experienced kernel panics every time I'd execute a certain python script. I was a little bit surprised, since I've executed more heavy scripts before, but doing my research, I found out, that the Pi detected an undervoltage at boot time (at every boot). The warning would go away (no yellow flash in the corner, which I'd experience with another microUSB cable), but to be sure, that the Python script doesn't trigger undervoltage again, I set out to measure 5V-GND with my digital multimeter.
My multimeter has some very small measurement tips, which don't stick well to the GPIO pins, so I think, I might have broken something. In the beginning, not understanding the pin assignment correcctly, I measured between random pins. Then I found the correct pins 2 and 6. By that time, the Pi had already rebooted a few times, but it still came on again every time.
At some point during measurement, the Pi shut down and wouldn't come on again. Only the red LED is constantly on (but the ACT LED shows no activity at all). I've tried disconnecting any peripherals (other tghan the power supply, obviously) from the Pi and tested several other SD cards (including a backup that I've just made yesterday from my main SD card). No success. :-(
If I interpret the schematics correctly, the red PWR LED shouldn't light up at all, if the fuse F1 were triggered, right? However, the controller doesn't get hot when powering the PI, either. I read that this could be the case, if 5V were supplied to a 3.3V GPIO pin, and the controller had consequently been fried.
Any ideas what else I could try or measure? I'll set up as replacement Pi tomorrow, but I'd be really glad, if my original Pi can be revived.