So, I have a MG1 that is mostly working. The only issue is…
Some keys decay while others sustain like they should. If it switched to auto, they all work normal. if i hold the key down below the key that decays, the higher key sustains like it should. Release it and the key decays abnormally. It seems like it is the same notes with the issue. Is that a part that controls sustain for a group of keys?
I can do solder work, but in the future. Anybody know anyone in the Pittsburgh PA area that will do analog repairs? I also have a farfisa that needs love.
Some oxidized, or dirty keyboard switch contacts. The keyboard contacts would need to be cleaned.
Fairly common problem. Those contacts are gold plated so use 100% isopropanol (isopropyl alcohol),and not stuff like “deoxit”. Unless you want to have to redo it every 4 weeks.
Also be careful not to bend those contacts out of shape.
Yep, exactly. You can find isopropyl alcohol (isopropanol) at any good drugstore (also know as rubbing alcohol). Just make sure it is 99% pure. Usually you will find 70% concentration easily. But they should also carry the higher 99% concentration. You might have to ask the pharmacist for it specifically. Be aware that it is extremely volatile, flammable, and toxic, so don’t smoke and don’t inhale the vapors directly while doing the cleaning job.
You can do a good job by using flat toothpicks under a small lint-free piece of cloth dampened with isopropanol. When it dries up (very quickly) you just buff each contacts with a clean and dry lint-free piece of cloth.
Don’t use Q-tips because they can leave some fibres in between the contacts. Take your time, don’t rush anything. It’s a relatively easy but time consuming process.
I finally have time and found the alcohol i needed to try to clean my MG1!
I do want to say, i don’t think I mentioned this before. It’s the same note across the keyboard. Is there a part/section that tracks the "A’s, B’s, D’s and F’s ? All the other notes sustain. Just to be clear… If I hold a lower note that does sustain, the aforementioned notes will sustain as long as I am pressing and holding that keys. Even if I pump the key, it will sustain on and off.
The fact that it the some notes makes me question if it’s a cleaning issue.
I’m trying to clean as we “speak”! I don’t see any change. Any repair I could send this to? I am at my end with this thing!
Is there a certain section where a key makes contact that causes it to sustain? I know that there are two metal strips that touch two wires that stretch across the keys. There is a long section of metal every few keys that if I touch it it sustains the missing notes. It’s the 6th metal strip in from left.
PLEASE HELP!!! Even if you can point to where I should focus, please do. Could there be one spot damaged or bent that keeps the others from working?
The way the trigger extractor circuit works is as an envelope follower that converts the sound of the notes from the polyphony into a gate signal according to the presence, or not, of a note being played.
In other words, check the polyphony. If there are some notes missing ( or even slightly softer in volume) than others, that might be causing some intermittent triggering of the VCA envelope in the mono section.
This would likely be caused by one (or more) of the divider chip failing MM5823N (common to MG-1 and other synths of that era using this type of technology).