Vintage Synth Repair

Hello there,

I bought an Arp2600 two days ago and there seems to be a little 
problem with the osc-pitch.

As long as I press a note on the arp's keyboard the tune stays 
stable. If I release the key, the oscillator pitch tunes down slowly 
without stopping. But, if I plug a dummy in the cv keyboard-in on 
any of osc, the pitch stays stable at 110hz. the keyboard is a 3604 
model, the arp is version 3.

Any ideas?

Another question: the jacks for patching in are 3,6mm instead of the 
common 3,5mm. can anybody tell me, where I can get those jacks, 
preferrably in germany?

Does anybody know who repairs analogue synthesizers like the arp in 
germany?

Thanks in advance.

Michael