Opto-Key MiniMoog Upgrade

Opto-Key MiniMoog upgrade

Synthfool’s Opto-Key Installed

The MiniMoog, along with many vintage synths, suffers from oxidization of the key contacts. It needs all keys to be pressed regularly to break the building oxidization, before it becomes a problem. The symptoms of the keys going bad are they become “squirelly”, i.e. multi-triggering, or dead due to not triggering at all. Another issue you see on keyboards is that as the keyboard generates CV from a resistance chain (1volt/Octave being common), any resistance in the contact alters the voltage out, thus frequency.

The folks at www.synthfool.com came up with an optical method of detecting key presses, called the Opto-Key. This incorporates a micro-controller in the Stripping the keybed for re-bushingdesign, making it possible for them to also add MIDI In/Out. Jason, the owner of this early MiniMoog, decided that as it was in need of service, he would ask me to implement Opto-Key, rather than continue with the key contact clean regime.Removing the keys

The keyboard was re-bushed while disassembled for the upgrade, and I can report that it works nicely. A service was also carried out, and some pots View of Opto-Key controller and optical sensorshad to be opened in order to clean them and banish crackles. For reliability the disintegrating C280 “Tropical Fish” capacitors were replaced, the power supply re-capped, re-greased, and bridge rectifier replaced. All switches and open-back pots were cleaned, and the unit set to spec. Plays nicely now.


Ace Tone Rhythm Ace

Ace Tone Rhythm Ace

Ace Tone Rhythm Ace

I have an interest in old, analog, drum machines, and take them in for service. Sheldon brought to of these model FR-1 units in for service; one was in pieces, the other had gummed up switches, and was generally sad. The biggest issue I has was a lack of schematic, so if anyone has oneAce Tone Rhythm Ace FR-1 to share I would appreciate it. They also wired the boards into these units in a way that makes it extremely difficult to work on them. A full service was carried out on both, and both were fully re-cap’d as one had low volume, and the other excessive hum.

Ace Tone Parts ReplacedThere was also a severe crackle on one unit that was traced to a Ace Tone Internalsnoisy germanium transistor, that thankfully NTE had a replacement for (NTE103A). You had to adjust the bias afterward, but the pot fell apart on touching it, so that was replaced and all was well.

Roland Juno 60

Roland Juno 60This unit needed a deep cleaning session and service.It was disassembled and cleaned-up, with fluff etc vacuumed away.Juno 60 Key contact fluff The sliders and volume control had switch cleaner applied to cure the crackles, and key contacts were cleaned. One bank switch was not working, so I removed, opened it, and cleaned it. The battery was replaced, and FCO applied for dropping into manual mode (I have never had one come in that had Juno 60 FCO at Power Supply endthis dealer applied; it addresses the fact that the power to the front panels goes through a couple of small connector pins, and this was insufficient, so direct power connections are added). Patches re-loaded, and unit put on burn-in test for a week.

Korg MS-20

Korg MS-20 Restored

Korg MS-20 Restored

This MS-20 had sat in a basement for some 30 years, and was in a grubby state with corrosion on the jack nuts etc. One key was broken, and the power cable was damaged beyond use. I took it completely apart, cleaning everything, lubricating all pots and jacks. The caps were leaking, so a re-cap was performed. The customer obtained a replacement key from Japan, and I fitted that, along with a new power cable.


A benefit, and curse on the MS-20, are all the jack nuts. Korg MS-20 start of clean-upWhen you take the patch panel out, there is another set on a plate over the jacks to remove in order to access the circuit board. Korg MS-20, so many jack-nuts!The benefit is that these nuts can be swapped for the outer ones, the washers flipped over, and then it looks nice and shiny. The MS-20 came in looking sad, and not making a sound, after restoration it looked and played great!

Octave Cat Restoration

Octave Cat Restored, just needs knobs and switch caps

Octave Cat Restored

I have done various Octave Cat’s and Kittens, from the original version, through SRM II. What they have in common is that they are tough to get going, and sorting out the keyboard contacts is always a major pain. This one though was the worst of the worst. It had been stored in a bad environment for many years, giving it corrosion and a bad case of filth. Worst of all though was that the bottom was missing, and the buss-bars/keyboard contacts were mangled, along with broken resistor packs. It was missing 5 of the j-wire activators, and all of the knobs and slider caps.

It was stripped, cleaned, and gradually rebuilt. I managed to straighten out the buss-barsDirty Octave Cat and contacts, re-bush it, and hand-clean the keys. Everything was cleaned, and the sliders/pots/switches treated with switch-cleaner. Some of the switches had to be opened and Octave Cat Mangled key contactsdeep cleaned in order to get them working. Electronically, some CMOS chips had failed and were replaced. VCO1 would not run at its lowest frequency, and I could see that a previous repair attempt had changed all of the suspect chips, plus there were a lot of component changes/ additions. I was fortunate in that another one came in, so I could compare and put it back to standard, and fix the original issue!

Life was then repeatedly cleaning and adjusting keyboard contacts, and fine setting it up until it worked reliably, phew! We purchased some knobs from Frys, and found that Sam at Syntaur has the slider caps. Doug at Synthparts thankfully had some of the j-wire acticators