Circuit Bending Part III

A lot has happened since the first two posts, I have reached new levels of creativity and ingenuity in this DIY art form. Or as some may say, I've just tried to make something useless work. In Circuit Bending Part II I only wrote a brief summary of what I did with the Casio ML-1. Check out these pictures to get a better idea of the inner workings of this crazed instrument.

Also, there are pictures of the homemade oscillator I made with a friend. After he was impressed with my initial 'creation', we decided to make a simple sine wave generator. Researching for schematics of these circuits online and using a unique electronic software program allowing the user to draw in circuits and run them, we decided on a diagram using a 555 timer chip, a few resistors, and a capacitor. A 555 chip (all integrated circuit chips have a numerical code) is a programmable timer that converts the incoming voltage into a constant output of frequency. Using the proper resistors, a frequency in the audible range can be obtained. Probably not the most exciting thing, but you somehow feel accomplished when you made a box that can change pitch. A potentiometer allows for variable resistance of the voltage, and therefore alters pitch. We used 2 single pole switches to select 2 different type effects we were able to get by bending our 555 circuit. A plastic roker switch was made an I/O switch for the 9V battery power, and a 1/4" output allowed for connection of headphones.


Homemade 555 oscillator



Still thirsty for more bending, I purchased a Casio PT-87 off eBay to explore and see if older toy keyboards were similar in circuitry design. When I unsheathed the board from the plastic, I wasn't surprised: it was strikingly similar to the ML-1, just with a smaller sound chip (only 8 sounds on it, ML-1 has 25). I enjoyed the sound of it, and was content with leaving the sounds untouched. ALthough I had no use for the ROM cartridge slot, as those are very rare and I didn't want to look for one. I did want to be able to use it in the studio more though, so I added an output. Not TS or TRS however. XLR. Female. Stolen from a broken mic cable, I drilled out a hole large enough for the XLR plug to fit sung and for the ROM slot cover to close all the way. A harmelss bend, but a functional one in the least.


Casio PT-87



The ease of circuit bending can be exemplified by the vast scale of the toy instument market in the late 80s and early 90s. Keyboards, guitars, orchestral instuments, even talking calulators and learning toys were huge among kids. Years after, benders are taking the industry in a new direction. Vintage gear of this fashion is so easy to find- my mother bought a Casio PT-100 she found at a garage sale. Users have outgrown the toys, or their kids grew up, or they're tired of the kids making so much noise, they sell them. Don't believe me? Check out ebay, theres every kind of toy keyboard imaginable, including ones that already are circuit bent.

So the PT-100 I received came with much excitement- I had heard how this particular model was great for alien synthesis. The item seemed to be in good condition, even came in the original box. Turned on once, and the sounds worked as normal for seconds at most. Then came silence. Even test bending it all over the PC board did nothing but 'pops'. It does have a nice 3" speaker, useful parts and a nice enclosure going for it though.