Zed's Dead, Baby

This here is a Casio CZ-101. It's often mistaken for a cheesy home keyboard that you might give to the child of a friend you don't like for xmas, but while diminutive in size and in original MSRP, it's actually a genuine, professional music machine. You'll find no button that plays a corny samba rhythm, nor will you find any onboard speakers; instead you'll find some 1/4" output jacks, and a pair of full size MIDI ports on the back.

Along with some strap buttons so you can wear it on stage like a keytar.

Now this particular example has two problems. First, it doesn't make any noise (and not just due to the lack of onboard speakers). Second, it's absolutely filthy. It also has some condition issues that are common with a keyboard that people mistake for a kid's toy.

I tried to send the ghost of this astronaut back into orbit using a bit of rubbing alcohol, but that just ended up taking off some of the finish where the sticker's adhesive had long ago softened it. I suppose the spaceman has left his indelible mark on history, and this synthesizer will forever wear the scars of its past life.

Anyway, let's get down to business. Click through the link to follow along.

To get anything done in here we're going to have to get inside, so out come the screws on the bottom side to reveal the juicy innards.

And of course the wires to the battery compartment which are soldered in place, because of course they are.

I'll be dealing with that later. For now they just get desoldered so that the two halves of the case can be fully separated.

Once we're in, the culprit for the lack of sound is easily identified: the volume slider is dead, with no conneciton between any of the three pins. I'm not sure I've seen a slider fail so spectacularly before, though I have seen this on a few rotary potentiometers that were literally broken in half.

Luckily this slide potentiometer is still produced, it's an Alps Alpine RS30111A602N which I picked up on Mouser for the low, low price of $3.30.

Out with the old and in with the new.

Perfect, shiny solder joints, just how I like them.

Next task on the list is cleaning. As I said, this whole synth is absolutely filthy, so much so that I'll have to strip it down to its bare chassis to get it properly clean.

There's quite a few PCBs inside here, and they're all soldered together with ribbon cables. This kind of construction isn't uncommon for the era, and it tends to come apart not unlike field dressing a deer. You just pull out what's loose until you run out of slack, then reach in to loosen up the next bit.

And there's a lot of "loosening up the next bit" as evidenced by how many screws I had to remove.

And that's not even all of them.

Unsurprisingly, the keys are going to need the most attention, so it's time to break out the borax to break up the grime.

With just a little attention from a soft bristled brush, and the power of borax, the keys are looking fantastic.

So that's the keys and contact strips cleaned.

Next up are the buttons, and it pays to stay organized since they're not all the same.

Though part way through reassembling them I noticed that the special buttons were actually called out on the inside of the case.

And amusingly some of them were actually called out wrong when they made the mold, so they had to cross out the incorrect marks and engrave a corrected set next to them.

While we're dealing with the case (which also got a bath in the borax), now would be a good time to glue this black key guide post back in place, which I hadn't realized was broken until I disassembled the keybed. Luckily the post itself was still rattling around under the keys.

Alright, everyone pray to the gods of the glue that this fix holds.

And with that, the case, keys and buttons are refreshed and ready to go back together. How much dirt did I pull off, you might wonder?

A fair bit, I'd say.

So on with reassembly. The button contacts and black keys go in.

Followed by the white keys and the key retention brackets.

And then the various PCBs get reinstalled, in much the same way as one might stuff the entrails back into a field-dressed deer.

With that out of the way, we're into the home stretch. I just need to deal with the annoying battery leads, and I'll be using this JST pigtail to do so.

The battery leads get pins crimped onto them.

Then they get shoved into the connector shell, giving us a solderless place to separate the wires.

Of course this won't do us much good if the pigtail isn't soldered to the board, and that's easy enough to do.

And now the battery wires are reconnected.

... backwards. Oops. Well, that's easy enough to fix with a quick re-do of the soldering.

In any event, the synth can now get reassembled as everything is back in working order.

It makes sound again, and is much, much cleaner than it was when I got it.

I should note here that it does have one minor issue remaining, which is that the battery door is missing. I don't plan to use batteries with this synth, though, as it eats 6 C-cells at a time with a voracious appetite, so I might just ignore it forever, or I might at some point work up the pathy to model and 3d print a replacement. Only time will tell.