After a few days of nagging Pharmasonic and many users of the Muffwiggler forums, I have managed to troubleshoot the 1st of my problematic modules, the 707 Amp/EF/Integrator, and this process has uncovered problems in several of the other modules as well.
It turns out the LM301 opamp IC’s that I bought are bad. These are in several modules, including the VCO’s, S&H, and the Noise/Ring Mod. I’m hopeful that replacing these chips will allow the Noise module to work fully, and I can then move on to testing and troubleshooting other modules.
It is apparently common knowledge among synth builders that 75% of components from China are bad. I’ve been discouraged from ordering chips off eBay in the future. In the meantime, I’ve asked for a refund on the chips from the eBay seller and am treating all other IC’s and transistors ordered from eBay as suspicious.
I have a Mutable Instruments Shades arriving tomorrow, which should be able to produce a +10V signal, which I need to calibrate the VCA’s. There are some ‘suspect’ 3080 IC’s in those, so testing them should help me determine if these IC’s are also bad. Once I know that, I’ll order new LM301’s and 3080’s (if needed) from Jameco, which has both in stock and is a US-based supplier, so getting these shouldn’t take 3-4 weeks.
Once the LM301’s are swapped out, I’m hopeful that 4 of the 16 modules will be working, which will include the Multi, Mixer, Amp/EF/Integrator, and Noise Source/Ring Mod.