Cgs synth

Well I am pleased to have my first CGS Serge module wired and powered up - CGS83 positive slew. The top half is working fine and is very cool, but the bottom half fails to oscillate when neg pulse out connected to start or sustain. I have been comparing voltages between modules at various points and the biggest clue is that neg pulse out is 6.61 V out on scope with no connection back and pulses look good on scope but the bottom half is sitting low at 1.781 V and fails to pulse no matter what I do. Checked wiring, all transistor orientations, all passive components look matched, replaced LM3900, same result.

I know it is a long shot but I would feel better if anyone whom has built this could confirm PCB layout worked fine on bottom section of panel. I see only minor differences on all banana jack ins and outs - for example output sits at 0.144 volts dc on good section but 0.178 on bad one so it is hard to understand how neg pulse out could be so different.

Anyway, in summary if you have built one and confirmed PCB layout is fine for bottom half of panel, please let me know just to rule that out. Any suggestions on best troubleshooting techniques welcomed, I will trace wiring and components around neg pulse out meanwhile to see why the output is low.

Thanks guys

Gord