Casio SK-1: Overhaul, Part One

Tuesday, October 8, 2013 at 2:42 am

Casio SK-1 (artist's rendering)

This is part of a series of posts about the Casio SK-1. For more, see the introduction page.


Stage One: I Accidentally A Pattern (Intro)

I’d had a long day at the office. I wanted to mess about with some music stuff, but I figured I was too wiped for any sort of serious effort. I decided to dig out my Casio SK-1, which I hadn’t used in ages. After a bit of messing around, I decided to record myself playing it, then went to sleep.

The next evening, I found myself in the same situation: tired, but still wanting to do some musics. I played the SK-1 for a bit, then recorded myself playing it. Again.

When the situation repeated itself the third evening, I realized I’d “accidentally a pattern,” and decided to keep going. I created a soundcloud for it. I made up a set of rules for the project to keep it on track: Sample whatever beforehand, do a bit of noodling to warm up, then record it, maybe with some aux effects. No more than one a day. Try to do it daily; but OK to skip it.

After about two weeks, I’d been all over the thing — gotten around to all the more obscure functions, like additive synthesis and the built-in sequencer (“memory”). My SK-1 was circuit bent, but only ever so slightly: three switches; that’s it. Worse, it was grungy. Dust in all the crevices, someone (possibly me) spilled beer on it a few years ago, and so on. None of these things had bothered me before, but now that I was doing A Thing, I increasingly felt need to do the SK-1 justice. I wanted to make it owsum. So, I put SK-1 Jams on hiatus, and promptly got in over my head modding the thing.

More below the cut.


Stage Two: Pre-Mortem

A word on planning: I suck at it. I didn’t have much of a plan going into this beyond “add switches, make more different noises.” I wasn’t even going to do a blog entry, or take pictures of everything. Once I arrived at the notion “The SK-1 does not have enough switches; I must add more switches” I carried it over to the workbench. I took a few pictures so I could do a before/after slashup, then cracked it open. Very quickly, I realized a few things: It was dirty, all over, and cleaning it was gonna be a major task. I would have to take it apart. Thinking about that, I realized taking photos was going to be important, in order to help me remember how everything went together. Once I had a bunch of photos, that also became A Thing. I realized I was laying the groundwork for a blog post, which I guess makes this post the byproduct of emergent complexity.  Bottom line: here you are, reading a blog post that exists solely because my SK-1 did not have enough switches.

Once I’d disassembled and cleaned the SK-1, I began studying it. I found the service manual on the ‘net, along with lots of bending advice. Afterwards, I simply couldn’t settle for just a few new switches; much more needed to be done! Three weeks and at least 40+ hours of labor later, I still have not actually gotten around to installing any switches. O tempora; o mores. The trite cliches I have at my disposal don’t feel quite right: Did I get in over my head? Did I bite off more than I can chew? No! I can chew this, it’s just going to take me way, way longer than I expected it to. Frustrating as it is to have the project’s time demands explode exponentially, I’m OK with it. I think this is actually where you want to be: the project dictating its terms to you, rather than the other way around. I could have just left all the dirt on it and hastily bunged in a few switches, but that idea displeased me. After I made the decision to do things “properly,” I handed over decision-making to the project, and it went all kid-in-candy-store on me. C’est la vie.

Here’s my SK-1 in its “original condition”:

Casio SK-1 (Dirty) Casio SK-1 (Modded, Bent)

Gross outside! How is it inside?


Plenty of grunge in there, too. Foam on the power cable is super gross and disintegrating. I have no idea why I wrote “TOWELETTE PETTITUCI” in there. There is way too much wire used on the bends; did this before I really knew what I was doing. There is dried beer on the PCB. Way too complicated to spot clean. If I want to clean it instead of just ignore it, I will have to take the thing completely apart….

…fuck it, let’s do it.

At this point, I start to feel like I’m restoring a classic car. I carefully disassemble and document the SK-1. Parts of it were in surprisingly good condition, while other parts were straight out of a horror movie. A hairy one.

Casio SK-1 disassembled inside


Stage Three: Intensive Denastification

Cue the cleaning montage!

Dirty Q-Tips

Cleaning dirt/beer off of the PCB.

Casio SK-1 Membrane Switches

Also these.

SK-1 Bath

Spa treatment. How’s that retr0brite stuff? I could use some…

Casio SK-1 (Drying)

Never mind the dishes; SYNTHESIZERS.

Casio SK-1 Buttons

…and buttons.

Stage Four: Figure Out What I’m Actually Doing And Do It

Once everything was apart, cleaned, and dried, I spent a good deal of time staring at all the parts and researching things on the internet; boiling down what I was going to do and how I was going to do it. Taking the SK-1 completely apart was more than a tad nerve-wracking. I’m man enough to admit I had a couple screws left over by the time I put it back together… but, it did allow me access to hard-to-drill areas. This was fortunate, given the amount of stuff I decided to put in: Individual channel outputs. A connector to let me get to all the bend points (without gutting the speaker and replacing it with a patchbay, as most do!). Other things too, which I’m going to keep mum on for the moment…

First was a 25-pin parallel-port style connector for all those juicy bend points on the ROM/RAM chips.

The Dremel Connector
SK-1 Connecta
Lots of wires
SK-1 port

After that, began putting in jacks for the channel outputs:

SK-1 Temporary WiringTemporary wiring. Instead the tape balls are electrolytic caps (decoupling).

SK-1 channel outputs

Physically installing jacks; floating wires.

SK-1 SolderingMore temp soldering for the channel outputs. Realize a jack is bad; replace it.

SK-1 Ribbon CablesRe-Soldering these took a lot of patience…

SK-1 Proper WiringWith everything in place, I decided to reroute things and cut out excess wire.

Next, I wired up the connector to the bend points on the chips. I also put the back cover/battery wires on an extension cable with a connector, so it can be easily opened and/or removed entirely. This is super helpful when working on it! Speaker also has a bit of a wire extension, but you can’t really see that.

SK-1 Ribbon and Connector

Finally, putting back the original bends:

SK-1 bends and data/address lines

Stage Five: Close It Up (for now)

At this point, I was tired of working on it, and missed my daily SK-1 jams. Furthermore, I now had the individual outs — giving me some renewed jamming possibilities — and the data port, which I could use to explore bends without it being on the workbench. Both my gut and common sense yelled at me: Play with it now! No point putting in switches until I’ve found good points, and I can use the data port to experiment all day long. So, the switches (and some other things!) remain for a Part Two.

For now, though, close ‘er up.

SK-1 Modded
SK-1 individual channel outputs

Stage Six: Fix Stuck Keys

Upon testing it out, I realized my rainbow ribbon cable interfered with the key travel. In particular, the black keys were very hard to play reliably. So, some final field mods were made, via clipping off a bit of the plastic with diagonal cutters.

SK-1 KeysIn general, the black keys have had it. Better than the white stripes, though

(seriously — can I get replacement keys somewhere?)

Stuck PadSome of the pads were also snagged, preventing them from triggering properly.

Fixing this, I noticed something really weird. There was a light shining from within! A diode was glowing. Not, like, an LED, just a regular diode…

wtf glowy diode

wtf glowy diode

…is it supposed to do that? Did I short something out? I don’t freaking know!

Aside from weird diode glow, however, it seems OK. Level outputs work like a charm. Nothing seems broken, which I regard as a small miracle.

Stage Seven: Appreciation / Gestation

SK-1, Done -- For now.

The individual outs make recording it loads easier: no more way-too-loud drums!

Now that the data port is there, I can build an expansion box at some point… and for now, treat the connector like a very tiny patchbay.

…and it’s clean. Sort of.

Update: Here is a video of me testing the patchport connector! It is a 150mb MOV file.

Categories: circuit bending / SDIY, gear, Uncategorized

2 Comments on “Casio SK-1: Overhaul, Part One”

  1. Electronic musing is back!!

  2. Love the post and am going to have to check out some more. You sound like my brother from another mother 🙂 “It needs more switches…” love it. Keep on keepin on, chief!

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