Wavering CEM 3340 Vco's

[Nev]

Greetings synth-diy'ers.

There was a thread on this list recently about someone having problems
with some cem3340 osc's wavering in pitch which sounded very similar to
the probs I am having with my Crumar Spirit syth.

Heres my partciluar situation: I have manage to tune the VCO's by trial
and error using my ears, but there is a problem with the LFO's which I
don't know how to fix. They are switchable  from off to various
destinations eg pulse width pitch etc. etc. via the mod wheel. But even
with the mod wheel turned all the way down and with the LFO's switched
in, there is some " bleeding" from the LFO's which affects the VCO
pitch, resulting  in the wavering sound. When the LFO's are switched out
of the circuit this disappears. Any suggestions on this one?

Of course I don't have schematics and only a little experience in
electronics.

Cheers,
        Nev.