>Anyone have a schematic of the A500 keyboard? I don't think there's one in the manual
There are schematics in the "Introduction to Amiga 500" manual (some introduction). In the version that I have the keyboard pins 1 and 2 are reversed (found out the hard way-- experimentally). However, the reset and ground pins were correctly labelled. Try connecting the reset to the ground pin (carefully) and if that resets the Amiga, you know it's the keyboard and not the motherboard. Or if not technically inclined, try the Peripheral Simulator here:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320167447376If it works and allows you to reset your Amiga from the PC, it's not the reset line on your motherboard.