theres some snes schematics over on http://caitsith2.net/snes/ i dont know if theyre complete or not.. i'm not that great at reading the links between pages.. but there seems to be everything.
thought i'd post this since i was under the impression that they were pretty much impossible to find.
also i emailed the person who runs the page and found out that it's probably possible to interface the integrated version of the snes apu with a pc aswel.. i might try this sometime, but honestly i've been more into my cars than my games lately :x much the same reason you all dont have a switchless region free snes.
I've built one and man I love it.
The program is a bit basic but being able to for example load the sound bank of super mario world and play with the songs and sound efects is really fun :)