Korg Poly800/EX800 Users

Hi guys,
I've got an 87 poly mk1. I used to have one of these when they first
came out along with a set of korg midi pedals, a poor man's Taurus.

Anyway, I've done the battery mod and the slayer mod.
The cutoff control works great but the resonance doesn't seem to have
any effect at all. Am I missing something? Can anyone point to a
specific sound setting in the mk1 patches that it should have an
effect on?  All my wiring looks right and I checked for faults/dry
joints.