Crumar Musical Instruments User Group.

Greetings,

I am hoping someone may be able to point me in the right direction with regard to diagnosing the problems with my two different Bit One keyboards.

1) CEM version - this board was completely functional several months ago after an earlier repair, but now makes no sound aside from some filter resonance on some patches.  Replacing the battery and loading sound dump do no help. Oscillators cannot be heard at all.

2) SSM version - this one behaves as if I have the mod wheel on all the time, applying the LFO constantly.  Mod wheel has no effect.  All voices and filters are working, and if I disable the LFO via parameter 1, the keyboard is semi-useable.  Noise generator is not audible (although this is not critical).  Tuning is unstable sometimes.

Any suggestions as to which components to check or replace would be greatly appreciated.  I have access to a simple scope and meter, soldering experience, but only a basic knowledge of electronics.

I have a pile of spare chips for many of the parts that have gone bad in the past, or are plentiful on the boards.  No one in the region is willing to look at these keyboards, so I have to repair them or retire them, which would be just wrong.

Thanks for your consideration,

John