Vintage Synth Repair

Hello folks

Lately I've noticed the sub on the last voice of my cs50 totally disappears.  Sometimes it comes back but mostly its off.  I opened it up and scoped pin 2 of IC 9(IG00158 waveshape convertor), and there is no output.  The STI("input of the wave for producing the sine wave") input which is pin 15 of IC 9 does have a triangle wave inputting into it, and i'm assuming this is the input to the wave converter that gets filtered into a sine.

I guess my question is, since i see a signal going into IC 9 but not coming out does this mean that this chip is bad? or could there even be a chance that there is a loose wire somewhere causing this problem (i've fixed another cs50 where the soldering job from the factory was a joke) and this could explain why sometimes the sine works?

I want to add the other waveforms coming out of this chip are ok...
thanks if anyone can help
Greg