Vintage Synth Repair

Hi,  picked up a Roland SPV-355 pitch to voltage synth module from a
friend recently and it's turned out to be faulty.

Basically the VCO's dont appear to be doing much..the mix sliders
VCO1, VCO2 and sub VCO dont do anything, however you can get some
sound out of it which is basically oscillation from the filter I
think..as according to the SOS review "The SPV355 features a
well-specified voltage controlled filter, a 24dB/octave type with a
range of 10Hz-20kHz and the ability to self-oscillate, in which case
it becomes a third VCO"

The triggering side seems to be ok as you can make the self ocillating
filter sound by playing a guitar into it or hooking up cv/gate. It has
no relation to the pitch but then I dont expect the filter oscillation
to react to pitch like the proper VCO's would.

So basically I think the pitch to voltage side, triggering etc is
fine..I just think the VCO's aren't doing anything..

Can anyone advise? The basic question is: What would stop both VCO's
from sounding?

I have the service notes if anyone need to see them, also it appears
to use similar architecture to the Jupiter 4 or promars..it uses
UA726HC's.