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MINIMOOG!


analogman1

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I still can't believe it...somebody pinch me...

If you all recall, I had been ranting a while ago about how I should have **NEVER** sold my old Moog to a family member, etc.

Well..one of my students found a used moog, and just surprised me with it!

It sounds awesome..except for one thing...once it's warmed up it basically goes a little nuts. So, I'm reaching out to all Ye experts at hand..does someone know of a competent tech who can give this baby a "once-over" and get it back in shape? A few of the pots are noisy as well...since it didn't cost me anything, it seems worth it to put it back in shape. Any thoguhts?

Oh, did I mention it came with a Calzone Flight Case? :) I'm still thinking this is a dream! (an anaologue one, of course) :thu:

Tom

Nord Electro 5D, Modal Cobalt 8, Yamaha upright piano, numerous plug-ins...

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You have to narrow down what you mean when you say that it "goes nuts", Big T.

 

The first thing I would do is to open it up and look for cracked solder pods/junctions. Take a soldering iron and reheat them & inspect them again just to be sure they're solid.

 

I would probably use a can of compressed air and blow out any dust.

 

I would buy a can of Caig Deoxit and spray on those pots to quiet them down.

 

As you know, the Moogs were notorious for going out of tune and 'going nuts' regard to pitch changes during/after warmup. There may be other people here who have had direct experience fixing that problem. It may involve replacing ICs, caps, or a discrete transistor or two. I don't know. If you could find a schematic, that would surely help.

 

If all else fails, pack your bags and take a trip to visit us in beautiful North Carolilna. Dr. Moog lives and works in Asheville. Perhaps he could lend you a hand. :)

 

Is There Gas In The Car? :cool:

"Music expresses that which cannot be put into words and that which cannot remain silent." - Victor Hugo
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If your Mini needs service I can recommend:

 

Kurt's Amps & Keyboards

1133 Boulder Park Ave.

Prescott, AZ. 86305-1422

http://www.kurtsamps.com/

This guy is a huge Moog fanatic. Kurt sevices all kinds of vintage analog synths including modulars.

 

Kevin Lightner

1486 Desert Front Road

Pinon Hills, CA 92372

Phone: (760) 249-6767

E-mail: synthfool@synthfool.com

Another highly regarded Moog technician. From what I've been told Kevin isn't doing as much as he used to. Check with him on his availablility.

 

Advanced Musical Electronics

8665 Venice Blvd.

Los Angeles, CA. 90034

Phone: (310)559-3157

advancedmusical@attbi.com

Former factory authorized service center for Sequential Circuits, Oberheim and Moog in Los Angeles. Works on all vintage keybpoard stuff including Rhodes and Wurlitzer. AME is good with just about any vintage board you can think of.

 

dBm Pro Audio

320 West 37th St. 5th fl.

New York, NY 10018

phone: 212-629-0326

jrfrond@dbmproaudio.com

http://www.dbmproaudio.com

Known for servicing vintage synths and keyboards, including Rhodes, Wurli, and Clavinet. They claim to do Moog restoration.

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Yup, GTRBass is right.

 

I was checking out the Moog website. They don't service your antique in Asheville. ;) If it was built before 1996, you should send it to one of the guys on GTRBass' list.

 

Good luck!

"Music expresses that which cannot be put into words and that which cannot remain silent." - Victor Hugo
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Hey Guys,

Thanks so far for the suggestions...."Is There,...", I should have clarified...what I meant was "goes nuts" was basically it just plays at random pitches; it kinda sounds like someone twisting the tune knob really fast. HOWEVER, I've had the thing on all day now and it seems to have settled down....it's holding a perfect tuning so far...so maybe it just needs to be played to get back in shape. But I will do all you said to try cleaning the pots, and getting rid of the dust. "GTR", I will probably call dBm Pro Audio soon, and see what they can do for me to make sure everything is cool. Thanks so far for the great ideas.....

Anyone else out there care to chime in?? :)

Tom

Nord Electro 5D, Modal Cobalt 8, Yamaha upright piano, numerous plug-ins...

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That was the problem I had when I sold mine. It was the contacts and the contact bar. Never could get it fixed so I got rid of it, just before Moogs became popular again. My problem was not being able to find a good repairman, and not having a source like this forum to locate one.

This post edited for speling.

My Sweetwater Gear Exchange Page

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Originally posted by Rabid:

That was the problem I had when I sold mine. It was the contacts and the contact bar.

Rabid, it's funny you mention that...a couple of times, it did the "pitch dance" just after I pressed a key in the middle. Don't know if it was coincidence or what but I'll make a mental note of that.

Tom

Nord Electro 5D, Modal Cobalt 8, Yamaha upright piano, numerous plug-ins...

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Yup Big T,

 

If my memory serves me (fat chance of that!)... there is a particular sub-circuit within each oscillator circuit that has the job of keeping the pitch constant as the unit warms up. I wish I could explain it better, but it would take all day and a decent schematic.

 

However, the problem with analog electronics - as you probably know - is that they can be hyper-sensitive to silly things like: age, dust, dirt, grime, leaky capacitors, hairline cracks in the circuit board, attention from pro football cheerleaders, etc.

 

Most often with digital circuitry, it either works or it doesn't. But with analog stuff, it gets interesting, and dirt is the #1 culprit. Age is not kind to analog-based oscillators. Get someone to check it out and bring it back up to spec & you'll have a keeper.

 

Oh... Is There Gas In The Car? is kinda long. I know that. It's just a great line from a Steely Dan tune that I like a lot. Many folks shorten it to ITGITC? or just Gas. Mom calls me Tommy. My friends call me Tom... but I've been called worse. :rolleyes:

"Music expresses that which cannot be put into words and that which cannot remain silent." - Victor Hugo
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Actually "going nuts" is a pretty good description of what they do. I had one for about ten years and almost invariably the 'going nuts' problem had to do with the contact bars under the keys. Before you take it in, try cleaning those really well.

It's also old enough that the gold plating on the contact bars may be corroding a bit.

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Originally posted by Is There Gas in the Car?:

Mom calls me Tommy. My friends call me Tom... but I've been called worse. :rolleyes:

Same here, my name's also Tom. "Big T" just kinda stuck through the years...had it been "little T" I might not have liked it so well! :D:D:D

By the way...it's been a few hours and the Mini is still rock solid...not drifting at all....maybe it "fixed itself"?? :idea: Nah, I'll still have a tech bring it back into "fighting shape"! :cool:

Tom

Nord Electro 5D, Modal Cobalt 8, Yamaha upright piano, numerous plug-ins...

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Originally posted by Steve in KS:

Before you take it in, try cleaning those really well.

It's also old enough that the gold plating on the contact bars may be corroding a bit.

Thanks Steve...is that a difficult thing to do?? Are the contact bars easily accessable once you open up the synth?

Tom

Nord Electro 5D, Modal Cobalt 8, Yamaha upright piano, numerous plug-ins...

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Take off the bottom cover(6 screws around the perimeter of the bottom and 2 toward the middle on mine). This will expose the bus bars and the contact springs. Take a small brush with isopropal alcohol to clean the bus bars. Play each note and work the bus bar area and the springs controlled by that key. Be EXTREMELY careful not to stretch the contact springs. The springs might need a little cleaning as well. Probably best to spray them with deoxit. If these are not making good contact with the bus or is stretched laterally across the bar that creates the pitch voltage when the note is played this is when the pitch goes nuts. Some of the springs may have stretched(misformed) from use or improper maintenace. Last I checked each spring goes for $5.00 Each note uses 2 springs contacts and its a bitch replacing them. I've done it several times.

 

Do a search on this forum. Someone did a better job describing all this stuff a while back. Cleaning it is easier then I made it sound.

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Some of the other folks mentioned the contact bar and cleaning which sounds good, but using it helps too. It doesn't hurt to "work" each pot back and forth if its been sitting a long time.

 

 

Mike T.

Yamaha Motif ES8, Alesis Ion, Prophet 5 Rev 3.2, 1979 Rhodes Mark 1 Suitcase 73 Piano, Arp Odyssey Md III, Roland R-70 Drum Machine, Digitech Vocalist Live Pro. Roland Boss Chorus Ensemble CE-1.

 

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Marky, thanks for the info, I'll give it a try soon....Mike, thanks for your input as well...I noticed that just playing the heck out of the thing is doing wonders....

Tom

Nord Electro 5D, Modal Cobalt 8, Yamaha upright piano, numerous plug-ins...

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Update:::

It seems that when I leave the Moog on for a little more than an hour, it settles down and holds pitch perfectly. So I'm starting to believe it is "a particular sub-circuit within each oscillator circuit that has the job of keeping the pitch constant as the unit warms up..." as "Is There Gas In The Car" had suggested. Any other opinions?

Tom

Nord Electro 5D, Modal Cobalt 8, Yamaha upright piano, numerous plug-ins...

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Originally posted by analogman1:

Update:::

It seems that when I leave the Moog on for a little more than an hour, it settles down and holds pitch perfectly. So I'm starting to believe it is "a particular sub-circuit within each oscillator circuit that has the job of keeping the pitch constant as the unit warms up..." as "Is There Gas In The Car" had suggested. Any other opinions?

Basically, that is pretty accurate. Here is a little more technical explanation: We generally want oscillator pitch to respond to a control voltage something like 1 volt per octave. However, an octave is a doubling of frequency, so we really need an exponential relationship - a doubling of frequency for each additional volt of control voltage. Diodes have a very excellent exponential relationship between the voltage across them and current through them (the most perfect exponential in nature), and are therefore used in the design of an exponential amplifier that feeds the oscillator. However, the equation for this relationship has a temperature component in it, and therefore the amplifier is very sensitive to temperature variations. This is usually compensated for in two basic ways: First, using a component (resistor or diode) that has (approximately) the opposite temp coefficient, to cancel out the temp variation in the exp amp, and second, heating the diode up to a constant temperature (sometimes even thermostatically controlled) so it doesn't vary (much). I'm guessing the first technique is used in the Minimoog. So, as your synth gets warmed up (literally!) and the temp stabilizes inside, so does the frequency of the oscillators.

 

Whew! :eek: Hope that helps?

 

- Bob

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