Korg MonoPoly

Korg MonoPoly
Korg MonoPoly

This MonoPoly had the worst kind of problem when it arrived: a very intermittent problem. It had a tendency to fade out randomly, and then randomly fade back in. The first day it was here, we ran it for 12 hours continuously without any such incident. It took us a long time to figure out what was going on because it was hard to get it to replicate the problem.

This synth is pretty cool but I am really pretty frustrated by how ugly it is. I’m imagining that there was a product design meeting and someone was like “OK and let’s make the oscillator section knobs white” and then someone else was like “NO! That’s not dreary enough! Better make them a wretched green-beige.”

After taking a detour to work on the VCA envelope generator, we discovered a really exasperating issue. Every pin connector on the whole synth was glued together– probably a couple dozen Molex connectors glued shut with some kind of hard green glue. Some synth companies will seal Molex connectors with a small dab of glue that has to be cut with a knife the first time it’s serviced, but this was something else as they were absolutely filled with glue. I’m not sure what issue they were seeking to preempt by doing this, but at the same time we realized this, we also realized there was intermittency on one of the pin connectors of the power supply that was responsible for distributing +5V throughout the board.

korg monopoly connectors glued together
are you kidding me??!!

Though that problem was fixed by just reflowing the solder on the pins, the glued-shut connectors make me nervous. My desire to fix up the synths I work on in a way that is reliable in the long term makes me frustrated to have to leave it this way as it eliminates the option to clean pins of connectors in the future, should oxidation creep in. But it is clearly impractical to redo all of them now. It would cost hundreds of dollars; they would all need new Molex connectors, and some of them would need all new wire as some of the current wires have been trapped by the glue, and would not be long enough after being cut.

Please, never use glue to strengthen any electrical connection! Please! It reminds me of the time another local “repair shop,” which I shall not name, attempted to glue a failing DC jack together in a friend’s synth.

Work Done: replaced power supply capacitors, cleaned scratchy volume pot, replaced transistor and dual op amp in VCA envelope generator; tracked source of intermittent failure to bad power supply connector, reflowed and added solder.

One thought on “Korg MonoPoly”

  1. Hi, I really like this blog.
    Yep… that crackly green glue on the ribbon connectors is factory.
    I’ve had a few Poly-6’s and they all had that.
    Not sure how much help it was as those connectors had a physical clip to keep them in place.
    Best regards and keep soldering !!! 😀

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