Circuit Bent Fun Years Keyboard

Yesterday I decided to take a break from In The Crystal Palace and mess around with some new toys instead. On Saturday I picked up some used kiddie electronics at the Salvation Army thrift store, including a Fun Years keyboard. A cheap Chinese knockoff, this toy keyboard has some interesting features, including several rhythm settings, a record button, and a "one key note" button. The electronic guts are what you would expect to find - a "black blob" IC common to most inexpensive electronics, and a separate amplification chip. To change the pitch I removed the timing resistor & and replaced it with a 500k potentiometer. I also added two photoresistors so that the pitch can also be altered by light/shadow. I also poked around the amp chip and found some nice distortion and feedback bends. Finally, I added a 1/4" output jack.

Overall interior view w/ modifications

View of pitch control w/ 500k pot & 2 photoresistors. Photoresistors are hot-glued inside a wood block which is hot-glued to the front interior case.

Exterior view of pitch controls. Photoresistors are above the knob.

Overall exterior view w/ modifications. The distortion/feedback bends are manipulated by the two knobs at the right.

I'm happy with how this project turned out. The photoresistors add an additional level of interaction and playability, and the distortion/feedback bends add some teeth to the audio. For example, there's a cheesy "Mandolin" setting that repeats the same note as long as the key(s) is held down, but slowed down & distorted has an ominous, driving Krautrock vibe.

Here's a short video clip:

and... here's the same clip but with the video scrambled using Audacity, slowed down 90%, and edited in length to fit original audio:

Circuit Bent Casiotone CT-460

So my latest circuit bending foray is a ca.1987 Casiotone CT-460 keyboard that I picked up at the local Goodwill for 15 dollars. A quick Google search led me to a pdf of the user's manual, and a couple of circuit bending sites and youtube videos. After verifying that the thing still worked (via slightly balky 9v adapter plug; I rewired the battery connection to accommodate a 9v battery & added a kill switch) I pulled the back panel to take a look at the circuit boards. I poked around a bit & found tons of bend points associated with the chip just to the right of the main cpu (blue box in picture below).

I found that most folks who bend Casiotones put together a box of banana jacks (one jack for each bend point) that can be connected by a lead wire with two banana plugs that are also connected to a potentiometer. Next step, though, is to identify all of the bend points and solder wire leads to each - I found 42 points, plus an upper-pitch point (the two red wires in the second photo below).


Wires are then threaded to box attached to side of Casiotone and soldered to the banana jacks. Solder solder solder:


Finished box with everything soldered in place, and two sets of lead wires. Bend points are linked to the grid of 42 plugs at the top, and the two connecting plugs to the 100k pot are at the bottom.


Here's a clip of the finished keyboard demonstrating the rhythm function using the "16 Beat 1" setting - I also made a temporary 100k pot connector out of an old tuna fish can so I could play around with a second set of lead wires:



Next up is a Yamaha PSS-270 keyboard. Stay tuned...