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03 December 2018

Modify a MicroKorg into a desktop synth

I bought a MicroKorg off eBay, and got it cheap because 10 of the keys didn't work. It's always a gamble with "as-is" tech that's sold for parts, and this time, I lost. I was hoping it was just dirty contacts, since the MK looked kind of beat up. I figured that since it worked otherwise, there weren't any bigger problems than the contacts, and I could always use a MIDI keyboard if I had to.

When I opened it up and took a look at the keybed, I found that an old liquid spill had eaten away at the traces. There was some bubbling under the surface, and tiny bits of the copper traces had long ago flaked off. I did attempt to clean the board and re-connect the traces with conductive paint (and failing that, solder) but it wasn't meant to be.

Whatever it was, it was still kind of gummy. I think it was beer.
Here's a closeup of the broken traces. I could see the spaces when I held it up to the light.
I decided it wasn't the end of the world if I chopped off the mini keys and turned the MK into a desktop unit. Since that's probably why you're here, I'll get right to the steps.

Here's what you'll need for this project:
  • A radial arm saw or something that will cut straight. Really.
  • An electric sander or sanding block for shaping what you don't cut straight
  • A drill, with appropriately-sized drill bits for your screws
  • Some scrap wood, about 1cm (1/4") thick
  • Wood moulding or something for the front panel
  • 12 small 1mm thick washers--I used some from a "pop-rivet" kit
  • Various wood screws--at least four, two shorter screws and two long enough to get through your front panel
  • Wood stain if you want to do that
  • Maybe four new rubber feet, since you'll lose the front feet
  • Probably your MicroKorg, otherwise why bother

Step 1: Gut it.

Seriously. Unscrew and remove the wood cheeks. Take the base off, disconnect the two molex plugs that connect the Pitch/Mod wheels and keybed to the MK proper, and take the main board out of the case. We'll be cutting the plastic case, so we don't want random bits all over the circuits. There are plenty of disassembly videos and walkthroughs online, so have at it.

You don't have to remove the metal panel with all the knob labels, so there's a small comfort.

Step 2: Measure twice, cut once.

You only have one case to work with, here, so be careful. Looking at the top of the case, there is a lip across the front above where the keys were. I used that as a guide, marking off a straight line across the left side where the Pitch/Mod wheels were, and the right side, where there's a slim part that the wood cheek is screwed to (don't cut the wood cheeks yet, remove them!).

See how the lip comes down behind the keys? We want to keep that. Also, this MK is fully assembled. Don't be that guy.
The cheeks are something I'll address later--you'll have to trim them down, just not yet.

I used a radial arm saw to cut from each side because for some reason I actually have one. I was a little generous on my cut on the left side (you can see the extra bump in the photo below), and needed to sand down some extra plastic. When I was done, the top lip stretched from side to side. That's going to come in handy later.

You may have noticed I didn't remove the MK's innards. Be smarter than me.
The base is the same thing. I foolishly tried to score it with a razor, but my cut went crooked. I'd recommend that if you can saw it along a straight guide, do that.

Step 3: Make the front panel.

I used a piece of oak moulding from a hardware store for this. It's a little over 1cm thick and already bevelled. I measured across the case to make sure that when I cut it, the front panel would be flush with the left and right edges.

Once it was cut, I had to trim off another 8mm or so from the bottom, leaving about 1-2mm sticking up (and down) past the plastic case, like the wood cheeks do. I sanded it smooth, since the plan was to stain it in an attempt to match the original wood cheeks (I was marginally successful using a cherrywood stain, though I think Korg were going for walnut originally).

You can make it whatever height you like, of course.

Step 4: Fit it all together.

Without the keybed in place, the plastic case has nothing in front to keep its shape. If you tighten the four front screws, the top cover will collapse inward. To counter that, I used four small washers stacked together to make a spacer for each of the screw posts in the front. Once I had that figured out, I reassembled the MicroKorg.

You can see the washers I used to keep the top from bowing in, as well as the unused Molex connectors for the Pitch/Mod wheels and the keyboard. Those you can just tuck into the case.
Here's the full length. I've already cut the wood cheeks, but I cut them for a thicker front panel that I ended up hating.
An article I saw elsewhere said to drill holes into the screw posts and use those to mount the front panel. I didn't want to weaken what's already a rather flimsy plastic case (and also aim so precisely), so my solution was to cut three wood pieces from 1cm (1/4") thick scrap wood to use as mounting blocks.
Literally one screw holding it at the bottom.
They're 3-4 cm wide, and tall enough to span from the base to the top when wedged inside. I had to cut a notch into the top of each one to make room for the mainboard--it comes very close to the front of the MK. The front panel will actually screw into the thicker part of the wood spacer.

Here's one of the wood spacers in place (the notch is on the other side at the top, against the mainboard). Notice how the spacer is only screwed into the bottom panel--the top is held in place by the plastic lip.
Here's the spacer with my original, too-thick front panel in front of it, hole drilled and ready to go.
I used a single screw to screw each wood piece in place from the bottom of the MK, trying to keep the wood 1-2mm in from the front to account for the overhanging lip on the top panel. That didn't work too well, but it's all inside, so whatever.

I marked the front panel about 3cm in from each side, trying to keep them centered vertically, and drilled some small screw holes. To countersink the screw holes, I used a larger drill bit, a little thicker than the diameter of my screw heads. Then I attached the front.

I took this photo after it was all stained and reassembled, but you can see the inset screw.
The screw at the bottom of each wood spacer keeps it in place at the bottom, and the lip on the top panel of the MK does the same for the top, pulling the front panel in without having to drill anything into the top panel. It's all sturdy enough to give you something solid to mount the front panel. With just two screws holding in place, I can carry the MK around by the front panel.

I reattached the cheeks and marked off where to cut so they stuck out about 2mm in the front (you can see that in the photo above). I then taped them back-to-back and sawed them off, using an electric sander to round off the top front corners. Then I measured about 2cm from the bottom and 2.5cm from the front, and drilled new mounting holes, using the larger-drill-bit technique to sink them. That way I could use the original screws.

I screwed the back part of each cheek in place and used double-sided tape to keep the front from moving once it was lined up, then drilled through my pilot hole into the plastic case. Using the original mounting screws (you'll have a couple longer screws left over from pulling the keyboard if you want to use those), I attached the front of each cheek.

The original hole, upper left, and mine, lower right. I didn't want to drill into my front panel for I don't know why.
That's it. Most of this is done to your taste, so if you want to use something else for a front panel or replace the original cheeks or add a PEZ dispenser, that's yours to decide. I think the only thing I really have to add to the larger "MicroKorg mods" conversation is my solution for mounting the front panel as invisibly as possible, and maybe warn you about the case flexing without spacers.

I did have a third wood spacer in the center, but screwing into it would put the front mounting screw off center (there's a screw post just to the right of center, so it would be a tight fit). Luckily, the two screws seem to hold the front panel on tightly enough that I don't have to offend my aesthetic by having a single, off-center screw in the front.

Ready to rock.
I'm sorry I didn't take more photos, but have fun modifying your MicroKorg!

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