Casio CZ-1000

The modified zombie synthesizer

I found an old synthesizer in my father’s cellar. Unfortunately it had been flood damaged. It’s been sitting down there in terrible condition for a decade or so. I figured it was dead.

It was found floating in muddy water. Can you tell?

Before trying to power it up I took it apart to see what I was dealing with. The only apparent problem is some corrosion around the power jack on the right hand side. It still had batteries(6 D cells!) in it when the flood happened so this makes sense.

Cleaned up the corrosion with an old toothbrush and some WD-40. WD-40 is a great cleaner for stuff like this and won’t damage a circuit board.

Sprayed DeoxIT into the power switch as this appeared to be corroded as well. There’s nothing else obvious in here.. let’s hook it to the bench power supply and see what happens…

IT WORKS. Not only did it power on but EVERY SINGLE KEY AND FUNCTION STILL WORKED PERFECTLY. An absolute miracle! The only real issue is one dead pixel column in the display. I can live with that.

The original power jack was toast. I ordered a new one from eBay for $5.

Might as well clean this thing up.. Yuck. Pardon the icky workbench - the keyboard wouldn’t fit on my soldering desk.

Supercapacitor modification

There’s one VERY annoying thing about this keyboard. Any customized sounds are stored in battery-backed RAM. You have to keep the 6 D-cell batteries in the keyboard or whenever it loses AC power it will forget everything. I have it open, so why not add a supercapacitor to power the RAM when AC is disconnected?

Analyzing the schematics in the CZ-1000 Service Manual shows that pin 9 on this ribbon cable is the RAM power supply and should be around 3.6 volts. Mine reads 3.8 which is close enough for equipment of this era. After testing I concluded that this is indeed a good place to connect the supercapacitor.

The drain is sort of high. The supercap will power the RAM for minutes or hours but certainly not days. Still, this is much better than losing all memory the millisecond power is lost.
EDIT: It lasts at least 48 hours! Horray!

Supercap (Blue, bottom-center) soldered to pin 9 of the ribbon cable and ground near the new power jack. I put some putty over the capacitor’s leads to insulate them and zip-tied it in place.

Results: The keyboard can remember its settings without AC for quite some time.

Here’s a video of the finished project in action: