Doepfer

Hi all, this is my first post!
I just got a small a100 system, and already I am faced with a problem;
today when I turned "her" on, the 106-1 has lost the ability to 
resonate. The Res. knob does nothing, and no amount of settings can 
change it.

I looked around the back and it didn't look as if I had lost any jumpers 
(that happens).

Any ideas on how to troubleshoot this?
Cheers.
Andreas Wetterberg