I have been eyeing it for a while, now it’s a done deal. The unit is in fair condition, quite a bit dusty, the rightmost key is broken. The inside has been cleaned before, and the unit has been fitted with midi (i’m told), 4 extra switches and 3 knobs.
After proper warm up, all keys respond and all electronics appears to work pretty much as advertised, except most pots are scratchy. I open the unit to see what I am about to clean and refurbish to an unknown extent. Alright, here’s the keyboard, and there the top panel, with the controls… but where’s the synth??? Almost by accident i discover an elongated circuit board buried under a bunch of wires. Is that it??? Oh man, there’s no more than 5 components (the 5 IC’s in fact) i don’t have as spares in my electronics box.
Not that much to do from the inside. A good keyboard cleaning. Lots of pots to clean and or replace on the top panel. Ideally, if I can identify some good replacements, I change it all. So I got to wait on this a bit, an go with a minimal keyboard cleaning and repair, and test the machine some more.
From the inside, that does not look like midi, with only two wires on pin 2 and 4 (din-sync?) of the midi jack, no apparent midi-2-cv circuit in sight. One retro-fitted switch is attached to the midi jack. One other retro-fitted switch has a nice effect on the filter. The rest are un-identified for now.
Has anybody seen similar modifications? I sure would like to find details about those custom mods. Please post links on the MG-1 if you have some. I’ll be surfing too. Thanks.
Try the service manual first. Most of the synthesizer is on the same board with all the sliders, the bottom board has the power supply and poly section.
Link here: MG-1 Service Manual
Thanks to the person who scaned this and made it available. Thanks!
Posting a photo of the unknown extra board/boards may help identify.
Thanks CZ, that will come in handy, or maybe hopefully not
You got me there. When I noticed how dusty the sliders were, I thought immediately about replacing them all. Easy job on a PCB with only pots and switches, which I thought it was. So I decided not to go see up there and avoid shaking the old wires downstairs for no good reason. So the synth is up there. Hummm…I’ll have to wait for the time being. The broken key is fixed and the unit back up with more screws than it had only a few hours before.
But I think I’ll open her up again… yes i need pictures.
Thanks latigid… it could be midi then, according to your pin out, wires are on 4 and 5.
Everything is not as good as I thought at first. All keys work and generate tone, but there something wrong in key mode. Envelopes work but the keyboard is not consistent in contoured mode. I heard some sound out of polyphony, but again, keyboard problems. It’s possible the unit has been modified for midi use only, excluding the keyboard, problem seems with the gates. On the good side, both voices, noise, bell, all controls work fine, the sound is gorgeous and free (as much as can be) of background noise. This thing really hauls.
Upon closer inspection, the sliders have been changed, they are now smooth and noiseless, so maybe there’s no need to change them. The rotary pots on the other hand are bad, but I think I am covered, with just the right pot for the main volume anyway.
So I think I am going to go for a medium scale overhaul right away. Maybe a reworked keyboard will solve the gate problem. I don’t want to keep the midi-2-cv if CV gate and pitch are working, there’s a possibility I remove it altogether. I will replace rca output with 1/4 inch jacks. And if I can at all, I wonder if it would be possible to add 4 inputs CV’s (connected to the pots or something). That would be real nice.
I’ll be satisfied if I can turn this into a CV controlled synth, from a remote keyboard, as long as I got clean Osc’s to drive my amplifier. That’s the plan for now. I wonder what it will be tomorrow
I did not expect a smooth ride by any means. I consider myself lucky just finding one with some potential. The latest in short :
Midi : Given the fact that the (apparent) midi has been installed for a while, and the results I came up with while searching the web, the midi adapter could be a Synth-jack. At any rate, it does not work.
I tested the unit with a CV sequencer, works well. From there a midi keyboard attached to a midi-2-CV gave similar results. The midi was supposed to replace the keyboard, but somehow, there was the same problem as with the keyboard, sometimes. I was quite sure I had diagnosed the keyboard malfunction right. Why then here too? Subsequently I discovered that the Detune slider in the tone 2 section has been hijacked to some other purpose, one of the retro-fitted switch controlling it. The keyboard always works well when the slider is in the upper portion of it’s range, and that applies to Tone 1 as well, even though this slider would not have any effect on the original MG-1.
I have had some time to enjoy the tonal characteristics of the MG-1 (and i’ll keep it one more week for more of the same), but given the mods I would rather see go away at this time, and to correct some other problems (still no polyphony lately) it’s time to go into complete overhaul and bring this thing back to original state. I want to know the machine inside out. This is fine and it is going to be fun doing. The only thing that bugs me is i don’t know how long it’s going to be out of commission.
