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...