After some very helpful assistance from some of the folks on the Muffwiggler forum (and Pharmasonic), I’ve determined that all the LM301 opamps I purchased off eBay are bad. I found 3 opamps that I had ordered for the S&H and Mixer units in my 1st round of work on this project that LM301 compatible, and I was able to drop those into the Amp/EF/Integrator and successfully get the amp to work. These LM301’s are also in the Noise Source/Ring Mod module, so I suspect that that is the cause of the problem with that modules’ ring mod circuit not working. The good news is that this means that the Amp/EF/Integrator, Noise/Ring Mod and, S&H modules are all officially ‘working’ as soon as new chips are dropped in, which is probably the least difficult fix that I can think of.
In other news, the 3-pin headers arrived and I’ve managed to install connections to all the panel-mounted pots in the project. Some of these were very tight fits on the two-board modules such as the LFO’s. This allowed me to move forward with testing the S&H, which is now working (yay!).
This brings the pantheon of working modules to:
- Amp/Envelope Follower/Integrator
- Mixer
- Multi
- Noise/Ring Mod
- Sample & Hold
That’s 5 down, 11 to go!
I’m now working on troubleshooting the VCA’s, as those are the simplest modules that I have that make use of the 3080 IC’s, which also came from China. As every module I’ve tested with this IC in it hasn’t worked yet (VCA’s, LFO’s, and VCF’s), I suspect that these chips are also bad. I’ve asked for assistance in confirming this on the Muffwiggler forums, and am waiting to hear back about it. Both of these chips are available through Jameco, but the 3080’s are $5 each, and I’ll be needing at least 11 of them (along with at least 15 LM301’s at a more palatable $1 each), so it’ll be nice to be fairly certain about needing to replace them before hitting ‘buy’.