Circuit bending the Casio PT-100


I’ve had this keyboard lying around for years (I don’t remember where or when I got it), and after my first bend I wanted to dive a little deeper.

After experimenting I read the writeup at tablehooters and found the chord modes, rhythm select, and sustain mode. I find the prospect of adding functionality that exists in the hardware but simply wasn’t built into the keyboard really exciting. I couldn’t really add more keys and the extra tone selection seemed convoluted. I also read the noystoise article which hinted at a tone select function but couldn’t find it for the life of me. I did discover a fill button which I added on the far left.

sketchup model

This is the final computer model I’d made after many iterations, including one with a banked panel and many more switches and knobs. There’s a deceivingly trim-pot-type element close to the main IC which turned out to be a tank circuit so the pitch knob was out. I was also hoping to replace the six position volume slider with a knob but upon testing it picked up some conservative talk radio. After eliminating some similar bends and discovering the switched potentiometer trick–see below–I narrowed it down to 12 knobs on the upper panel.

In progess:

When I started this project I had very few tools and parts. So while I was waiting for the mail I was estimating the resistance range needed in a bend by the amount my 50k pot was turned. This article led me to believe I could simply limit the range of a pot by adding the appropriate resistors in parallel. That’s true, but what’s left out there is that doing so changes the relationship between knob turn and resistance to a more logarithmic one (see here). So using resistors to change a 50k pot to a 20k pot actually doesn’t add that much control to the sound (depending) and could even make it worse.

Dremeled potMany of the bends I found required switches but after learning you could hack a potentiometer to also act as a switch (see here and the picture) I thought it would be fun and a little nicer looking.

The hardest thing to solder by far was the reverb switch (called “sustain” in the tablehooters article). This involved soldering directly to an unconnected lead on the main IC, pin 90. I could always de-solder it if I messed up so the bigger challenge to me was getting that much heat near the main IC without Tape solderfucking up the chip. Maybe it was unwarranted. I ended up using tape and then super gluing the insulated portion of wire directly to the PCB so it wouldn’t yank loose…

Toward the end of assembly I noticed a few of the pots didn’t have great connections and a couple pots didn’t quite do what they had when tested. I re-soldered and fiddled hoping for the best, but really I felt like that was part of the whole putting-a-shit-ton-of-wires-and-knobs-in-old-electronics deal. Even when it’s finally assembled the process of discovery continues.

Here it is before I squeezed on the back cover:

Overall I’m very happy with this project. I made a lot of tiny compromises, learned a lot, it’s fun to play, and I didn’t totally break anything! I consider that a success.

I do have the specific bends documented and I’ll share them upon request.

{ Add a Comment }

I opened up a gifted keyboard and found an alligator clip and a potentiometer still in the case. So I started poking around and had a lot of fun! This is my first bent keyboard. I really enjoyed making this and I’m currently working on another more ambitious project.

{ Add a Comment }

Here is a nice little article at No Zen in the West about the tension between the personal and communal aspects of buddhist practice and how they play into the political sphere. I’ve observed a dangerous inclination for some zen practitioners to be sort of new-agey and have a hands off approach to politics and this article speaks to it well.

{ Add a Comment }

From this article: “The dharma is not an excuse to turn away from the suffering of the world, nor is it a sedative to get us comfortably through painful times. It is a powerful teaching that frees and strengthens us to work diligently for the liberation of beings from suffering.”

{ Add a Comment }

Ducks is a wonderful short comic.

From the author: “Ducks is about part of my time working at a mining site in Fort McMurray, the events are from 2008. It is a complicated place, it is not the same for all, and these are only my own experiences there. …Ducks is about a lot of things, and among these, it is about environmental destruction in an environment that includes humans. Thank you for taking the time to read it.”

{ Add a Comment }

This book is amazing. It presents an open and complex view of American history while challenging many unaccounted for assumptions in our collective understanding of history and in the way it’s taught in schools. I’m enjoying every page.

this is a book

{ Add a Comment }

Here’s Jonathan Tepperman in an excerpt from a recent World Affairs podcast:

I don’t think terrorism is an existential threat [to the United States] …because the number of Americans killed every year in terrorist attacks is vanishingly small. More Americans are hit by lightning every year than die in terrorist attacks. More Americans drown in their bathtubs every year than die in terrorist attacks. The number of Americans killed by terrorism since September 11th, 2001 is something like 100 or 150. It’s minuscule. And that’s compared to more than 40,000 Americans who have been killed in handgun incidents. And double or triple that figure who’ve been killed in car accidents. The existential threat, if it’s there, comes in overreacting, in responding the wrong way to terrorism but not in the terrorism itself.

And then there are a lot of scary trends in the world. There are a lot of countries that are behaving in scary manners today. None of these represent existential threats to the United States either. Not China. Not Russia. For the simple reason that The United States is so overwhelmingly preponderant today in terms of wealth, innovation, and in its military power, that none of these countries can offer real competition.

Now climate change. There’s a real existential threat that defines the idea of an existential threat. And political dysfunction. Gridlock. The failure of our legislative branch to legislate. That potentially represents an existential threat because until that is resolved in some fashion none of these other problems can be addressed.

{ Add a Comment }

“I can’t understand why people are frightened of new ideas. I’m frightened of the old ones”

–John Cage

{ Add a Comment }

From Rebecca Solnit in this article:

“Naïve cynics shoot down possibilities, including the possibility of exploring the full complexity of any situation. They take aim at the less cynical, so that cynicism becomes a defensive posture and an avoidance of dissent. They recruit through brutality. If you set purity and perfection as your goals, you have an almost foolproof system according to which everything will necessarily fall short. But expecting perfection is naïve; failing to perceive value by using an impossible standard of measure is even more so. Cynics are often disappointed idealists and upholders of unrealistic standards. They are uncomfortable with victories, because victories are almost always temporary, incomplete, and compromised — but also because the openness of hope is dangerous, and in war, self-defense comes first. Naïve cynicism is absolutist; its practitioners assume that anything you don’t deplore you wholeheartedly endorse. But denouncing anything less than perfection as morally compromising means pursuing aggrandizement of the self, not engagement with a place or system or community, as the highest priority.”

{ Add a Comment }