[HAM] Low C on manual plays pedal

[BO]

Hey all,

  HAS made me buy another M-3 yesterday (I now have 3 along with several
consoles). It has a problem with the lower C on each manual. 

If the lowest drawbar is in use on a manual, the lowest C on that manual
will play a pedal tone if any pedal has been played, except the C pedal.

Once the C pedal has been played, the problem goes away. If any pedal
besides a C gets played, the symptom comes back.

I looked at a schematic and didn't find anything that I thought was common
that might cause this type of problem.

Any ideas?

Thanks in advance.

Brent