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The Radio Shack Realistic ConcertMate MG-1
Moog MG-1 Analog Synth!

mg1mood.jpg (18944 bytes)


So, you're interested in the MG-1...

...A.K.A. The Radio Shack Realistic Concertmate MG-1, Model 42-4000
Having to scrounge for information regarding this little beastie, I decided why not devote a web page to it!
bulletWhat is the Radio Shack / Moog MG-1?
bulletWhere can you get one?
bulletThe story of my MG-1
bulletAre the manuals still available?
bulletWhere can you get parts? --> Sliders and switches are NOW AVAIALBLE!
bulletMIDI-to-CV Converters






Check out EBayer chipforbrains!


(MM5823N or EA5823N) ICs
Use Google to find them.
EBayer chipforbrains also has some
new old stock.


You'll want the
Try here.

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The MG-1

The ConcertMate MG-1 is an analog synthesizer built as a collaboration between Tandy and the original Moog Music, Inc and marketed by Radio Shack under the Realistic brand in the early 80's. Despite its being sold through The Shack, the MG-1 is all Moog. It even has the famous Moog ladder filter, making the sound unmistakably MOOG!
Before going any further, a word must be said about the company formerly known as "Moog." Right now there are at least three separate companies doing business with Moog as a name or with heavy Moog connections. Big Briar, Inc. is a company started some 20 years ago by Dr. Robert Moog, and it's the one "most respected" as being the rightful heir to the original Moog name. A "Moog Music" site was out there as well, and there is a Moog Custom Engineering, and constant bickering goes on about its right to use the "Moog" trademark and name.  Who's right? Who knows...What I do know is that the company which made the MG-1 is no longer officially in business. I believe it was eventually sold to Norlin, Inc. and is now gone.  (Note:  There have been problems reported with deliveries from at least one of the Moog-ish incarnations...See my Gear page's Moog section for one person's story.  Buyer beware!)
But enough of that, and let's get back to the MG-1.
The MG-1 started life as a Moog Rogue, but I'm not sure what the differences are between the two. Considering that the Rogue was "designed to be as inexpensive as Moog could make it," I'd be willing to bet that the Radio Shack version shaved even more corners. Betcha the Rogue didn't have the just-so-darn-awesome "polyphony" the MG-1 has, though. Judging by the pictures in Vail's book Vintage Synthesizers, it would appear that the MG-1 got the Rogue's innards but kept the keyboard of the Rogue's predecessor in the Moog line, the Moog Prodigy.

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The MG-1's Major Features:

31 note keyboard (F to C)
Monophonic, using a really bad organ sound to achieve "polyphony" (which, fortunately can be shut off at the Mixer)
Two tone sources / oscillators, square and saw waves
Oscillators can be synced or detuned
Pink noise generator
Bell tone generator (ring modulator)
A countour generator (basically attack/release, with a switchable sustain)
External ports for trigger and pitch
A whopping 50dB signal to noise ratio!
User's guide, service manual (service manual covers the principles of operation in detail, basic repair, tune up, schematics, parts lists, etc)
A more comprehensive list is available at: David Johnson's Page at Sonic State

Front Panel Controls (Left to right, top to bottom)

TUNING TONE SOURCES POT -/+ (flat/sharp)
POLYPHONY POT -/+ (flat/sharp)
TONE SOURCE TWO DETUNE SLIDER (flat) -2 - +2 (sharp)


Rear Panel

L/R RCA PHONO JACKS Allows the MG-1 to be inserted into a tape loop on a home stereo system
INTERFACE PORTS PITCH in. JACK Voltage from external source to set pitch of note to be triggered (1 V/Oct).  IN/OUT.
TRIGGER in. JACK Shorting triggers note (S-trig).  IN/OUT.
POWER POWER SWITCH SWITCH Turns the unit on and off; Auto contour LED flashes during normal operation.

  - Vail, Mark. Vintage Synthesizers, p.36. Miller Freeman Books: San Francisco, 1993.

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Where to buy...

Where can you find yourself an MG-1? Probably in thousands of attics or basements by this time. If you read the story of my MG-1, you'll find that you may come across one at a flea market really cheap. They are also posted in the various used keyboard areas on the Internet. I saw two on Harmony Central's For Sale list in January, 1997, and the cost was about $180 for one and $225 for the other, if memory serves me correctly.
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My MG-1...

Good ol' Serial Number 1066 must've seen better days. A friend of mine spotted it at a flea market in southern New Hampshire, and knowing that I wouldn't mind a good deal on a new toy, he picked it up for me. For $20US. Yep---twenty bucks.

When I got the MG-1 home, I plugged it in, and I was tooling around with it for what must have been hours. What a neat little beastie!

But all was not well. At some point in its lifetime, the MG-1 was either dropped on its face or had something heavy living or plopped on top of it. Most of the plastic knobs were gone (not a big deal), the sliders were bent (slightly bigger deal), and most of the sliders were in rough shape (yucky deal)---some didn't like to move, and some didn't work well. The case had a nice crack, too. All signs of abuse. Hey, at least it worked. Well, kinda...

As I was messing about with the MG-1, I noticed that certain notes played only after I'd played other notes, as if these "broken" notes needed to "ride the wave" of the previous notes in order to be heard. Huh? And as time went on, *more* notes became unheard. Not good.

I opened the case. Well, in addition to being used as a footstool for a lorry, this machine had spent some of its time in a swamp. Inside was a bit of rust, musty stuff, dust lions, and that kind of crap. The previous owner was obviously a smoker---smoke stains, matches, and cigarette butts were ample.

My first step was to dismantle everything. The MG-1 is a two board plus keyboard unit. All three were detached from the case, and a cleaning job took place. Most of the gunk is gone now---especially the foam cover for the knobs and switches, which disintegrated into a gummy substance as I took apart the unit. (I'm not even going to worry about replacing that thing---I just hope I don't have cancer now!)

Still those notes wouldn't play. What could be wrong...?

On a lark, I called Tandy. "Do you have the user's or service manual for the 42-4000, a synth you guys marketed in the late 70's/early 80's?" The woman on the other end of the phone almost laughed at me. No, she DID laugh. But she agreed to check, and--lo and behold--the manuals for the MG-1 ARE available directly from Tandy! I got them a few days later for about $25.

I purchased a multi-meter ($40) and began hunting. Based on what was in the service manual, everything was checking out, that is until I began poking at the MM5823N frequency divider chips on the board under the keyboard. Everything was -5VDC, no problem, except when I poked at the IC in the middle, I got .28VDC, -2VDC, that kind of thing. Uh ohhh... Upon further examination, sure enough it was the notes corresponding to this IC which were failing!

No problem, I'll replace the IC. It's a National Semi MM5823, which they didn't have. Fairchild didn't. Numerous places on the net didn't, either. The friend who found the unit for me said, "You know, I bet if you checked Thomas or Lowrey Organ sites, you'd be able to find it. I'm sure these were used in those puppies..." A few days later I got an e-mail from my friend asking me to try out a site for Keyboard Systems (now Organ Service Corporation), a site where one can find Conn/Kimball/Thomas/Lowrey/Farfisa organ parts...Including a retrofit MM5823!

I ordered two (about $25), borrowed a de-soldering station, an oscilloscope, and a frequency counter from this same friend, and went at my synth. The old MM5823 came out, and this retro (a board with three ICs and a red LED) went in. Power up. No smoke. Nice red LED. And the notes were back! Now everything worked!

But there was a quirk waiting with the MM5823 retrofit.  I noticed two notes not working correctly.  I later discovered (February '03!) that at least in my machine I had to lift pin 8 of the retro kit for the two notes to work.  All I did was bend the pin out of the way and not seat it in the IC socket, and things work fine.  This may or may not apply to your fix, but it's something to investigate if some of your notes don't work quite right after you've replaced an MM5823N.

And then there was another quirk with the MM5823 retrofit.  Apparently the output of those things doesn't sit well with the cheesy Polyphony sound generator, resulting in massively distorted notes.  Sigh.  So I got a "real" MM5823N from yet somewhere else (don't recall where), and all notes but 1 are working properly with the Polyphony.  Close enough.  (The synth part works fine regardless of the MM5823 used (the real one or the retrofit).)

One final MM5823 quirk came in from Dave R. in e-mail.  His MG-1 had (2) National I 815 25539-002 chips in addition to (1) real MM5823N chip.  So whoever was making these used some substitute ICs at some point.

Using the service manual and a few misc parts I got from Radio Shack ($20), I walked around the board and made whatever tweakages they recommended. The MG-1 was back in business and sounding as bratty as new. The Keyboard Systems retrofit didn't make any real change on the sound quality.

Well, that was a few weeks ago, and it's still in pieces on my dining room table (this is the kind of thing you do only when you have the time and the inclination). I need to tack down a few of the sliders (or replace 'em), go over the tweaking a bit more, figure out how to get the big Keyboard Systems retro chip to fit (it should, as there is plenty of room between the boards, but I might need to bend a few pins on the retro), and then button it up.

UPDATE:  As of late 2003, #1066 was buttoned up and back in business.  It's in good working order except for the sliders (which I'm too lazy to replace).

MG-1 #2

Not content to have just one, #3235 made its way to me from a guy in Texas who didn't quite understand what it was.  He was somewhat frustrated that all it played was one note when doing just the synth part (and that note he could never get to sound like a piano) and although it had organ-like polyphony, he didn't want the MG-1 because it didn't have enough keys, so how could he possibly learn how to play keyboards on it?  I attempted to explain what the MG-1 is, but he just wound up selling it to me.

Sure enough, the usual MG-1 fun began...

bulletThe goo.  Yep, this one had plenty of goo, too.  It's all gone now.
bulletThen, of course, after you clean the goo, one oscillator dies.  Fortunately diagnosis was easy.  On the main board, there are two CA3046N ICs in sockets (ICs U1 and U4 under the goo).  I swapped them.  Sure 'nuf, the "dead" oscillator came to life, and the other one went dead.  A few clicks over to DigiKey or Mouser, and I had the 3046 IC ordered. 
bulletFrequency divider.  Of six between two machines, I have replaced 3.  I replaced one MM5823N in this one with one of the old retrofits from Organ Service Corporation.

But then I discovered that the "bell tone" (ring modulator) was not working.  Eventually I traced it back to the yellow wire going from the lower PC board to the upper one--it had been cut!  Someone modified this synth to take the TAPE IN and run it through the Bell Tone slider, probably using it as a volume control to allow external sound to be processed by the filter.  Nonetheless, it's back where it belongs, and the 2nd MG-1 is getting buttoned up...again without new sliders (I'm still lazy).

I got kinda lucky with this unit, as it's in great cosmetic shape and has all its slider caps.  Now it's in reasonable working condition.

Great project, great sound, lots of fun!

So if you run into one of these for $20, snap it up. Be ready to spend a few dollars getting it going, but when you consider that one out on the net can't be had for anything less than $180 (with some on auction web sites going for over $300), you may just snag yourself a deal!

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Are the manuals available...?

I was able to order mine from Tandy directly, but Analogue-Heaven e-mail list member Stephen Hagen has informed me that Tandy no longer has the service manual for the 42-4000.  If you contact Tandy, they may have other manuals available, but you may need to prod them to look.  Chances are they're all gone by now.  I have seen the Service Manual on EBay.

Check out this site which may have scanned copies of the MG-1 user and service manuals.  It also has MP3s of MG-1 sounds.

Please note that I will not be able to make copies of the manuals for you at this time.

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Getting parts...

9/20/03:  One of the big problems with restoring an MG-1 is the availability of exact fit sliders and switches.  I have come across a source for these.
MG-1 Sliders and Switches

What's available:
bulletA complete set of 15 sliders, in labeled packages, ready for you to solder in
bulletSets of slider caps
bullet2- and 3-position switches

Ordering:  These items are available from EBayer chipforbrains who often has auctions running for these and more.  I have ordered from this seller several times (most of the time off EBay), and he is great to deal with.  Please tell him that I sent you.


2-position switch (ruler is in inches)
Picture of switches on left:  Top switch is 3-position, bottom is 2-position

Other sources:

Most of the MG-1's innards are available in Radio Shack---typical resistors, caps, pots, and so on. The tougher items, as I found out, are likely going to be the IC chips, now over 20 years old, probably long out of manufacture. Some suggestions I have:
bullet Organ Service Corporation (formerly Keyboard Systems)
Although mostly for Conn/Kimball/Lowrey/Thomas/Farfisa organ parts, it turns out that these guys may have retrofit ICs for your MG-1, such as the MM5823 frequency divider.
bulletFred McNiff's Site
Fred is a former Moog employee, and he has lots (and lots!) of parts to help you maintain your Moog synthesizer.
The part numbers listed in the service manual were unknown to the person I talked to on the phone. My guess is you'll strike out there.
bulletHarmony Central
Not only will you find people selling MG-1s, you'll find people posting stocks of Moog parts on their For Sale pages. Check it out! (Great web site, too...)

Resistors are not futile...

One of the biggest misconceptions about the MG-1 is all the sliders are 10K or 100K ohm linear sliders.  Nope.  Here's the list from the service manual.

If you're looking for replacement sliders or switches, see Getting Parts above.

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MIDI-to-CV Converters...

The only wish list item I had out here was a good MIDI-to-CV converter to allow me to trigger the MG-1 from my PC, and it turns out there several available:
Encore Electronics
JKJ Electronics
Kenton Electronics
Synhouse MIDIJACK Synhouse MIDIJACK Synhouse MIDIJACK for the MG-1 (and other synths)

I had heard a lot about the Kentons being good stuff. 

I visited the Encore web site, and their converter was a bit pricey (good, but pricey). 

JKJ I'd found a while back, but I lost their web address. They're in my area, oddly enough, but I'd made my buying decision before finding those guys again (they have rather functional stuff at good prices, from what I've seen).  

August 12, 2000:  I just heard about the Synhouse via e-mail (thank you, Rich!), and it's a small and inexpensive MIDI kit for monosynths.  It's the only MIDI kit which fits inside the  MG-1, in fact!  They have extensive notes on how to install their MIDI kit into the MG-1 and other synths (with more to come).

I decided to pick up a Kenton Pro-2000 MIDI-to-CV converter. It has two independent channels (for controlling my MG-1 and my recently acquired Minimoog). It was easy to set up and get going, and it has been working well in my setup! With the Kenton, the MG-1 really shows its stuff. One isn't limited to the short keyboard---I can use my Korg X3 to trigger the MG-1 in several octaves. It's very easy to get a Tangerine Dream-like sequence going on the MG-1 through the Kenton, making it a great combination for me! Note: If you are going to pick up a Kenton Pro-2000, be sure to get one manufactured in or after February 1998. There were several additions to the firmware which allows MIDI-to-CV control of several more instruments, not just two. Else you'll need to buy an upgrade.

The MG-1 takes the Kenton's output with no problems and no modifications. Plug and go! Use S-trig for the trigger and Volt/Octave for the CV scaling.

Setting up the Minimoog to be controlled from the Kenton is a rather interesting deal. The Mini isn't really set up to be driven externally, as its keyboard is always connected and serves to mess things up. There are two problems, and here's how I got around them:
bulletThe scaling is off. The Mini's oscillators are scaled to its keyboard, not the external CV input. Fortunately the Kenton has adjustable scaling, so I just matched up the Kenton with the oscillators in the Mini. Problem solved.
bulletThe keyboard is always connected. This is a problem, but I've gotten around it so far with no mods to the Mini. Basically I hit the lowest key (F) on the Mini to get it to have a good starting point and adjust the Kenton to tune the Mini properly. This allows the correct notes to be played on the Mini from the converter. However hitting the lowest key on the Mini preserves that note only for a certain length of time, after which it will begin to drift. Mine hasn't had this problem, but I hear it's something like 2 minutes in most Minis. Hitting the key again on the Mini keyboard restores things for another 2 minutes (or whatever). I've found this an interesting feature, though, as hitting keys on the Mini will shift whatever's coming through the CV input by that many notes. You can change keys by hitting keyboard keys! :-)

Quick Thanks... the Synhouse MIDIJACK folks for sending me additional MG-1 information and corrections.

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