How Sound Selection works in the Yamaha CS-80

Yamaha CS-80 angled closeup of front

One of the things that has been the most helpful for me over the years in sort of syncing up my general understanding of electronics theory with understanding how synthesizers are actually designed is reading circuit descriptions in service manuals. A lot of the American companies especially wrote really great, detailed explanations of how their instruments worked, and reading them has helped me to both understand the specific circuits they discussed, and understand more broadly how different objectives in synth design can be achieved… and more quickly recognize what’s going on in an unfamiliar circuit.

Because I’m a nerd I guess, I thought it might be fun to make some step-by-step “circuit descriptions” like that for synth circuits that don’t have them.   My first featured circuit –the system through which the Yamaha CS-80 handles preset, panel and memory switching– is sprawling, but actually fairly simple, much like the synth that it comes from. Continue reading “How Sound Selection works in the Yamaha CS-80”

Restoring the Saddest Minimoog in the World

trashed Minimoog Model D

When this Minimoog Model D arrived a couple of years ago, it was probably the absolute most thoroughly wrecked synth I had ever agreed to work on. I made a deal to do it for a flat fee, even though I knew it wouldn’t be technically “profitable,” under the condition that I could take my time on it, kind of as an absurd challenge to myself and because I knew it would be really satisfying when I finally finished it. Since it is finally done and restoring it was such an insane gauntlet of tasks, I thought it might be worth reviving the long-neglected Shop Blog with a post about it! Continue reading “Restoring the Saddest Minimoog in the World”

“Don’t be that guy”

Roland CSQ-600: in which the tech replaced the NiCad memory battery but installed the replacement battery in a ziploc bag ziptied to the mains wiring.

One interesting thing about restoring vintage synths is that almost every instrument that we work on has been worked on by another tech at least once before. And it seems that more often than not, those other techs were… not great. We see a lot of bad work, but my favorite examples also feature a very special element of absurdity. Here are some recent highlights:

Continue reading ““Don’t be that guy””

ARP 2600

ARP 2600 circuit board work
We forgot to take a picture of it when it was done, so here’s a picture of it when it was dirty!

The owner of this ARP 2600 got it in an insane trade in the late 80s… in exchange for a Peavey keyboard amp and a TR-505! A lot of it had never worked in the entire 30 years he had had it.

When we do restoration of an ARP that’s in bad shape, we’ve learned that there’s really only one good way to approach it. We basically strip it down to its bones and do everything we possibly can in one fell swoop before even trying to test different systems. It ends up being so much more efficient that it actually costs less than taking a more step-by-step approach.

Continue reading “ARP 2600”

Rebuilding ARP PPCs

Using FSRs (force sensing resistors) to repair PPC "proportional pitch control" pads for an ARP Odyssey Mark III

Because I am now one of those people who thinks they are very busy, I am just going to share a “quick tip” today.

In one of several Odysseys that we rebuilt recently, the “Proportional Pitch Control” pads (otherwise known as PPC, those three spongy white pads that Mark III Odysseys have) were so bad that no amount of cleaning could revive them. I finally was forced to look for another solution, and tried using some FSRs (force sensing resistors) and the results were great.

Continue reading “Rebuilding ARP PPCs”

Moog Model 15 Modular

Moog Model 15 Modular Synthesizer
Moog Model 15 Modular Synthesizer (1974)

A Moog modular restoration is a very unique and specific kind of restoration experience, which I’ll try to show mainly in photos because it’s less boring for you. It will be like a vacation slide show with a fun anecdote to accompany each picture. Continue reading “Moog Model 15 Modular”

EML ElectroComp 101 – 1 volt per octave conversion mod

Update, 8/2019: we are now selling PCBS and kitsf that make it easy to install this mod! Click here for details.

This is a really fun synth! EML was a lesser-known American synth company competing with Moog and ARP during the 1970s and made some unique instruments. The EML-101 is a semi-modular duophonic synth similar in structure to the ARP 2600 and very unique and powerful. The bulk of our work on this involved designing and installing a circuit that allows the synth to accept standard 1 volt per octave-scaled CV via its “SEQ” input, as its oscillators have an unusual scale of 1.4 V/octave with a 4.6-volt DC offset. Continue reading “EML ElectroComp 101 – 1 volt per octave conversion mod”