Perfect. That’s the word we use to describe the sound and usability of a Moog MiniMoog. A first of it’s kind in portability and package, the minimoog took the most essential modules from the mighty Moog modular systems and hard wired them into a cabinet featuring a 44 note keyboard. History available online can show you the different models (A-C), however the one to note is course the instant classic minimoog model D synthesizer.
Just opening this Model D is proving a bit difficult. The screws on the undercarriage are both rusted and stripped. To make matters worse, the undercarriage is made of cheap particle board and is flaking all over my bench. Unsurprisingly, the particle board was destroyed as it was removed from the synth. One screw was left, and it could not be extracted without destroying the ugly flaking undercarriage.
After destroying the undercarriage during removal, I remembered that my friend Ken Rich had produced some ABS/plywood undercarriages for minimoogs to exact spec. Instead of cutting and routing a new one, I made a phone call and was able to grab one of the last ones he had available. I don’t think Ken sells these to the public and only uses these for his restored minimoogs he stocks in store, so I am quite thankful that I was able to get one.
Next on the do-list is the keybed. Usually when we rebush a keybed we take off the key caps and remove the old bushings with a pair of hemostats. When I looked into this keybed, it was clear that is was too far gone for that, and a full disassembly would be necessary, After all, this is going to be our store rental unit, so no reason not to go the full 9 yards. As you can see from the photo below… dirty is an understatement.
Besides installing a new set of our very own pratt-reed bushings, we also took out all of the “nubs” and cleaned and regreased those as well. This thing needed a good vacuuming and scrub down, but it all worked out in the end.
We decided to try something new and install the keys in a different order (starting on C) but it just didn’t work out due to the top note needing more modification than we were willing to do for this. We opted to keep it original. Once the keys were reinstalled, I have the bus bars a quick cleaning with denatured alcohol. I know they’ll need more work, but this way I’ll at least hear something.
Now the cover comes off, and all I see is glorious old moog boards inside… yes! We removed all the PCB’s and took note of the modification. Looks like a basic midi-CV ready mod, so I’ll let it live for now. I was pleased to find a broken switch inside where the “jack” was. This switch is surely the switch that toggles between internal CV and external CV control, and the PCB and trimmers on the modification are probably a CV tuner. I added in a new switch in it’s place, but will probably figure out a better solution, such as a switching jack. I have future plans for that hole it currently occupies.
Before we can power it, I’ll have Mike replace the power cord. Mike is my right hand man around the shop, and I’d happily concede he’s better at changing power cords than I 😉
It’s finally time for the first audio test… yes! I’m sure it’ll be quite out of tune and other things won’t be right. And I boy was I right! Worst of all though, many controls we’re very scratchy, and cleaning sealed control pots is no walk in the part either. They’re supposed to be self cleaning, as in being able to be “worked” into good operation, but this simply isn’t the case when they’re this dirty.
Instead of constantly reassembling this, I decided to just do the rest of the work I was expecting to do now, as believe me, this is not my first minimoog restoration :).
I started by [calling my wife and telling her I would be home late] recapping all of the cards and cleaning the metal-metal connections. Recapping was straightforward, as we have kits assembled in our shop that we sell on this website. It was nice to pull a kit and install it instead of dig through my drawers constantly. I am a proud user of my own product now I suppose!
The Oscillator Card
The best part of owning an old Minimoog is having the old style (technically the 2nd revision) oscillator card. It’s what separates the boys from the men, as far as minimoogs are concerned at least…
With a restoration in mind, the oscillator card is where most of the attention is needed. My favorite thing to do to minimoog’s is all on this card. It’s where you fix the errors present from the factory and where I add my special touches.
I don’t know what part of it’s existence caused this, but the sockets the transistor arrays were in were quite warped. Those were immediately replaced with choice sockets.
Next, we performed our full thermal compensation package involving changing the tempco positions and some opamps. This was partly inspired by some old documents by the late Kevin Lightner with some additions of our own. This package tremendously improves the thermal stability of the minimoog and makes it lock into tune almost instantly on power up. Some might think this takes away from mojo, but rest assured all mojo is left intact.
Besides thermal stability, we pay special attention to the tuning trimmers. The original trimmers are wire wound trims, and usually the “sweet spot” of tuning is indented from being set there for so long that it’s hard to retune them. Plus, it’s a wide variance over a single turn, so changing it with a trimmer capable of the same resistance but allowing 28 turns is a huge plus in precision and potential disturbances from physical movement. Some hot glue was added so they don’t wiggle so much while being trimmed.
Before bothering with powering it up to test for sound, I went ahead and installed our deadband kit to great success. The deadband mod is a moog factory mod (strangely omitted from the minimoog reissue) that fixes a very real issue. On a stock mini, the pitch wheel has variation at it’s center zone. This means if you tune the minimoog to A440, when you pitch bend, when you re center it, it may not be at A440 anymore… quite far off in most cases, actually. The deadband makes the center zone a dead zone where there is no pitch change for a small amount of travel. This is a sort of time consuming mod even though it doesn’t look like it at face value, but it’s so necessary, especially if you have sensitivities to things being out of tune. Now I can enjoy the creamy white wheels this mini features.
The First Jam
At long last, finally it is time to tune and trim this thing and see how it’s behaving. First thing I note is A440 doesn’t work. Quick fix was a loose polystyrene cap on the filter board where A440 resides. The power supply was trimmed after a 5 minute warmup and then the oscillators were tuned with their new 28 turn trims. This went luckily without a hitch. A few keys needed a good cleaning with denatured alcohol, but hardly anything to write home about. Thankfully it seems that this mini won’t need any further work to correct real errors. Everything is behaving as it should (thankfully).
On the cosmetic side of things, we’re going to go ahead and change the knobs missing their silver trim piece with some old stock used knobs and clean them all up a bit. Refinishing the cabinet is probably in the near future, but for now, we will leave this minimoog in it’s condition of very well working and proud of it’s age and wear.
Since it’s been mod’d to accept external CV, we’ll go ahead and stick with it to help it integrate into modern environments. The switch on the front is not something I am a fan of however, so I will be replacing its function by using switching jacks, and will add a dedicated triangle/square LFO with the rate control where the current int/ext switch is. I feel this is a useful mod and worthy of front panel real estate.
This synthesizer is available to rent from us and lives at our shop set up and ready to jam. Contact us if you’re itching to try the real deal!