Beware: Unintended short killed my MCU

This morning something has shorted on my printer and killed my 1284P microcontroller.

Basically it was reading the hot end temperature the same as the bed, as if they were connected together. Unplugging the hot end thermistor changed nothing (but should normally trigger an error and shut down) and unplugging the bed thermistor killed the hot end reading as well as the bed.

I first noticed he problem when the printer was reporting on 84 for the hot end, despite it being hot enough for plastic to ooze from. Who knows how hot it actually was, thankfully the peek didn't melt.

After much searching, pulling the electronics off and apart, and looking at the Eagle files for Sanguinololu, I found this thread:

http://forums.reprap.org/read.php?158,130513

Likely cause is a short between the 12V hot end resistor and the 5V thermistor, killing the 1284P's analogue to digital converter. I'll need to revisit the insulation around the heater to prevent a repeat.

Fortunately I still had my original 644P, so I reflashed it with the Panelolu commented off and the printer is going again.