Sequential circuits samplers

Hi everyone, first time poster here.  I powered up my old P2000 v3.0
today for the first time in years - it had a broken fuse holder and I
managed to source a replacement at last.  Lo and behold, it still
works (mostly)!  The disk drive isn't loading any old disks, but no
big surprise there - I'll go hunting for a new drive.

But the big disappointment - filter resonance is not working at all. 
Filter cutoff works, and everything else (including ROM presets and
all 8 voices) seems present and correct.  It's also sampling ok.  This
is a real shame, as the main reason I kept it was for the great filters.

Any help would be appreciated!

Cheers

Frank