[sdiy] Repair part question, Korg DDM-110/220 buttons

[Chromatest J. Pantsmaker]

Hello all,
This thread got me thinking about my DDM-220 so I pulled it out.
Everything appears to work on it fine except it won't play patterns.  When
I press Start, it will play the first step and then "pause".  I have tried
slaving it from my DM-110 and I get the same results.  At first I thought
something was holding the stop low, but now I'm thinking it's not getting
any tempo clock.  When set to internal, the Tempo LED does not light.  When
set to external, the Tempo LED tracks with the DDM-110's tempo knob, but it
still doesn't play beyond the first step.

I'm suspecting the 4066 is the culprit, or possibly IC-9 (4013) is the
culprit, but I'm otherwise unsure.
[image: image.png]



On Sat, Jul 13, 2024 at 6:39 AM Benjamin Tremblay via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Hi, I got me a Korg Super Drums off eBay.
> It looks just like the one I had in 1985 before I went crazy with the
> soldering iron and circuit bent the clock.
> It was DOA. I was about to give up on it when I noticed hairline cracks
> around one screw hole in the board. Was able to fix them and then it booted
> up properly.
> But it still seemed dead. Until I almost accidentally closed one of the
> switch contacts with a tool, and it responded. (In fact it’s so snappy I
> could be lazy and trigger the switches with MIDI via 4066 ics and it would
> probably respond at a high speed.)
>
> Looks like very fine hair and dust, like Persian cat dander, is coated
> around the knobs and switches.
> So anyway I found this link on polynomial showing how to crack the
> switches apart and clean them with a q-tip. I have some black goo I used to
> permanently fix an Alesis MMT-8 and so I intend to coat the rubber contacts
> with this good stuff.
>
> But just wondering: Does anyone know what kind of switch this is? (See
> photo on polynomial Repair Blog). To me it looks too good to not be an
> Alps, but it’s not a keyboard switch, is it?
> Whatever it is it’s kinda cool, as long as you don’t have cats.
>
> It seems like a lot of these kinds of parts have vanished from the storage
> bins and there’s nothing that would take its place.
>
> Ben
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