Vintage Synth Repair

Hi folks,

I'm currently working on a broken Hohner Clavinet/Pianet Duo board.
I've got a broken A/B switch, not working 9V input, a bad keyboard
selector switch and a general hum problem. As I understand many of the
Clavinet/Pianet Duos have problems with these things. Does anybody
here have experience with these repairs? 

I'm also looking for a place to find A/B switches.

Hope I can find some help here, I'll let You all know how it works out.

-Phil