Here are a couple audio demos of the recently repaired Sample & Hold circuit (more on that below) plus me gradually tweaking various knobs.
The MicroMoog is a 1970’s analog synthesizer, and I really wanted one when I was a kid. My mother would shop for sheet music at Portland Music and I’d play around with the Moog and Korg synthesizers. Eventually my parents bought me my very own MicroMoog for my birthday ($400 used). I learned a lot about electronic synthesis and had a lot of fun with it.
Since then I’ve moved on to digital synthesis, but I’ve kept my MicroMoog. Kept it in a closet that is. My brother was interested in taking a look at it and discovered that it was barely making any sound. He cleaned it up and then he and I spent a few sessions fixing it up. I’m very happy to report that it is now working better than when I got it. Not only is its audio amplification problem solved (new op amp and LM3080 “transconductor” ICs), but the Sample and Hold function is now working for the first time since I’ve had it.
The Sample & Hold can be used to produce random pitches, filtering and wave-shapes. I remember playing with it in the store and thought it was really cool, but when I got my synthesizer I was disappointed to find it didn’t work. My mom even helped me take it back to the store for repair but they couldn’t figure it out. Thanks to the Internet, my brother and I were able to download the schematic and service manual and troubleshoot the problem. We swapped in a new NTE467 Field Effect Transistor (JFET) that I bought from Fry’s for all of a $1.50 and then the Sample and Hold function magically started working for the first time since I’ve had it (over 30 years)! This was an exciting moment and one of the highlights of my sabbatical. Have a listen (near the top of this page).
We made a bunch of other improvements to the MicroMoog:
- Capacitors and 1/2 watt film resistors replaced with modern components
- Glitchy potentiometers and switches cleaned
- Pitch ribbon fixed
- Keyboard whisker wires and contacts cleaned
- Keyboard bushings replaced — the keys are no longer clacky and are waaay better
It was fun and impressive seeing my brother’s electronics skill in action. He’s been restoring old recording equipment during the last several years and his skill has surpassed mine somewhere along the way (not that mine was ever that great). His desoldering and soldering work is fast and tidy, and he quickly troubleshooted the audio output problem. It’s been great spending time with my brother during my sabbatical, and the MicroMoog is now working and sounding great! I do believe I’ll be integrating it somehow into my music (especially if I install the MIDI interface I ran across).
If you’re still curious about the MicroMoog, here’s a good audio visual tour of what the knobs on the MicroMoog do and sound like.