Moog Music Forum

Does anyone know where I can get a replacement mod wheel pot for my R.A.Moog Mini? From memory it's a 50k audio taper.

I've tried a few different modern carbon and plastic track ones but the log taper isn't as good as the original (too much mod early on).

Given the number of these machines in existence, there must be a source of replacements somewhere...?

Thanks,

I'd try AME:

http://www.advancedmusical.com/

I've seen Model D's in there before and they have TONS of spare parts. They'll get you going in no time.

Try Kevin L first...

synthfool@synthfool.com

He's got it all !

Sorry, not only do I not have these pots, but I cannot find them either.

Here's the problem....

The minimoog mod pot doesn't dial IN modulation, it shunts (shorts) it out. This means that the pot must go extremely low in ohms (1 ohm or less) when down or bleedthru will exist. Very few pots do this.
I've bought tons of different types, believe me. I have drawers full of various makes and simply put, they all suck.

Worse, the taper is very important. It's an audio taper 50K pot, but having specially ordered several of these from Clarostat (at $26 ea!), the taper of the ones I received wasn't quite correct either. There are several different log (audio) tapers available and not all will work as well as the stock one.

I don't recommend using a linear pot either. The modulation just doesn't act the same and can't get as deep. Using a smaller value (like 25K) doesn't help. It just doesn't feel like a normal Mini when played.

So, I can't help you. I can't even help me!
There are several tricks possible if you have bleedthru, but all are compromises or "band-aid" repairs.

Worse, I can't even order Moog type knobs any longer from the company that makes them.
The salesman I knew left his dept, no one knows me there now and crazier, waving thousands of dollars in their face didn't sway them a bit. They demand that I have an account first and require four verifiable credit references, which I can't provide.
I've asked everyone I know (Moog, Bucki, etc) and no one is willing to help.

With all this said, I've requested that Moog Music remove my name from this site as their only recommended US West coast vintage center. I can no longer do what I've done for years to Minimoogs.

Sad to Hear Kevin...

I remember you saying that the pot you put in my mod wheel was as close as possible but still not the right one.. And now the right ones ( the 26.00 dollar, not quite right ones) are all gone.. What ever you used in my Model D works great !!

- Nick

I honestly don't recall what I did to yours, Nick.
I don't think I used one of the $26 pots.
Since yours was a custom clear wheel job with the LEDs, I probably used an original. Maybe one from a scrapped Mini carcass.

Fwiw, Technology Transplant recently bought a mod section panel off Ebay. Since their business is duping parts for resale, their intentions might be to use that section to help make more parts.
If so, and they don't realize the specialness of that pot, they're in for a big surprise though!
Still, I wish them luck. Maybe someone will take the time to make the correct pots available again.

Btw, later Minis even had this pot further customized.
They added a silver coating in the pot to lower the end resistance even more. Very late production Minis even had gold plated connectors for the mod section.
All in all, it wasn't a very smart design, but it was for purely musical purposes and feel. This is also why so many virtual "minis" don't replicate a Mini exactly. A person has to use their own Midi controller and the mod controls don't impart modulation in the same way.

Did you ever try reconfiguring the mod circuit from a current shunt to a voltage divider? That's what I did to mine and I used a 25K linear pot. Maybe it changed the taper, but that bleedthrough reeeeeally bugged me.

Bummer about the Cosmo knobs...

BTW, those silver tipped pots were also used in micromoogs - can scavenge one of them.

I've tried the mod you suggest, MC, but it's just not the same.
JL used to do it too, I believe.
In fact, I once "undid" that mod from one of Devo's Minis because Mark couldn't play Smart Patrol correctly on it.

About a year ago, I reworked two of their Minis.
In one, I did add one of those custom ordered Clarostat pots, but I added a modulation depth control in the back as well.

To get around the bleedthru, I performed a trick:
On the wheel, I superglued a small magnet.
Across the pot terminals, I soldered a small reed switch.
Correctly aligned, when the wheel is all the way down, the magnet actuates the reed switch, shorting the pot out completely.
It's unnoticeable otherwise because the reed switch opens before any real modulation occurs.
Also, I recommend installing a heavy ground wire from the rectifier board's ground all the way to the mod wheel.
Sometimes it helps to also add a wire to the VCO board or if you're really adventurous, using one or two of the unused edge card fingers (cut a trace, add a contact flag) for an additional ground.
Moog realized long ago that disabling the sensing on the power supply helped because ground wasn't exactly ground where it needed to be.
This because the current draw is fairly stable in a Mini anyways and the additional contacts for the sensing can cause problems themselves.

Also, I replace ALL electrolytics in every Mini to reduce ESR and simply for reliability issues. I think it's crazy to see these guys who call their work "restoration" doll up a case really nice and leave 30 year old caps in the unit. I wonder if they've ever heard how good a Mini can truly sound.
Regardless, if someone uses the later VCO boards, the current draw is so great, there's much less reserve filtering. Three hot uA726's really suck current.

Also (as long as I'm rambling), many older Minis (likely yours, MC) have those dark brown resistors in them. In the modulation mix amplifier and power supply, they can cause additional buzzing and mod bleedthru. They're supposed to 5%, but I've *often* measured them at up to 30% off. Try measuring one or two sometime, especially some of the 820 ohm and 10K ohm ones. What's supposed to be 10K, might be 12.9K. I've seen 820's as high as 1300 ohms too.
So all those resistors on the PSU board that are near the finals, I usually replace with metal film types as well as any others in critical places.
Especially if a newer board is installed because the additional heat only makes them worse.

Some useful info there - thanks Kevin.

What about refurbing the original pots, is that feasible?

What about refurbing the original pots, is that feasible

Yes, sometimes.
It depends on the actual pot.

Inside, there's a solid piece of carbon that's used as the wiper.
If this is worn away, only replacement with another such piece is possible. Cleaning is possible and often beneficial, however I can't speak for anyone else's abilities. It is possible to damage a pot if disassembled or reassembled incorrectly.

If yours has bleedthru, I can't say cleaning will help much, but if it's intermittent, it may help.

Sorry I can't provide much advice. It's difficult to give specific, singular advice against a myriad of possible problems.