started bending my concertmate 300 (casio pt-1)

jamiewoody · December 17, 2009, 07:25:01 AM

i poked around with jumpers and discovered some kind of overdrive tones. not really fuzzy enough to be called distortion.

i added a pitch control simply by connecting the 3 leads of a potentiometer to the trimmer pot. this also slows down the tempo on the drum beats. kinda cool.

i connected two toggle switches to the "boost" bends.

unfortunately, i did not find a holy grail of glitch in this thing. i feel like i am just scratching the surface though.

i noticed a jumper next to the negative spring in the battery terminal. as i recall, in the sa-2 mod, someone stated clipping this jumper and adding a pot would be a power crash. is the same true with this keyboard? (i thought i would ask before trying that one.).

since there is almost no room in the box, i built the 2 toggles and one pitch pot into a small box, and made a snake for the cables in a heat shrink tube.

so, anything else tasty i can try?

jamiewoody · December 19, 2009, 02:20:35 AM

so far so good on this one. i really need to take pictures. i spraypainted the lid red, the well is white, and i took the white keys out and held the spray can nozzel part way and did a red paint splatter on the white keys! a real 80s retro look!

i almost thought it "looking cool" was as far as the coolness would go. i was for certain i lost it. but, as it turned out, it was the crap switch, typical of casio. the plastic switch with a tiny bit of metal, which scrubs a solder bump...self destructive engineering.

so, i soldered a pot to the tuning trimmer, thus, it has a pitch knob. also, i found a cool bend, a diode and a resistor, which turned it into a glitching, distorted, feedbacking mess!!! the switch and pot are wired series between the diode and resistor.

also, there are 2 more switches. one extreme trebble, to the point of distortion, and another switch gives it a bassier/darker tone.

the good thing about this project, was the fact that when switches are off, it is "factory" again. so, there are a variety of tones.

i am not finished yet. i think i will try a power crash mod. fun stuff!!!

Gordonjcp · December 19, 2009, 01:29:37 PM

Quote from: jamiewoody on December 17, 2009, 07:25:01 AM

i noticed a jumper next to the negative spring in the battery terminal. as i recall, in the sa-2 mod, someone stated clipping this jumper and adding a pot would be a power crash. is the same true with this keyboard? (i thought i would ask before trying that one.).

Why don't you look to see if the jumper is connected to the battery terminal? It's not hard to sit and trace out a circuit diagram for these things - you just need a pencil and paper, a good light to work in, and some coffee...

jamiewoody · December 19, 2009, 05:56:19 PM

coffee is a must! BLACK! dark roast!

i did see a jumper near the battery terminal. 2 questions: which type of pot should be used for the power crash? would 1k, 100k or 500k work? (i ask, those options, since those are what i have in stock).

also, is power crash possible with the power in jack?

anything else i should keep in mind?

jamiewoody · December 19, 2009, 05:57:10 PM

jamiewoody · December 19, 2009, 06:00:17 PM

hmmm...i don't know why this image is skewed. it is not showing the whole image either.

here is a link to the image. it isnt the greatest photography, but give you an idea of how it looks.

http://sevenismagic.webs.com/my%20synths/little-red-synth-vet.jpg

Gordonjcp · December 20, 2009, 12:00:56 AM

Using just a pot to do a voltage drop crash isn't a great idea. Try using a simple voltage regulator circuit instead - it will handle much more current than a pot will, and it will behave in a more predictable and repeatable way.

jamiewoody · December 20, 2009, 11:05:50 PM

what is an example of a voltage regulator? i went searching, and what i came up with looked like transistors. does it have a control like a potentiometer?

Remork · December 23, 2009, 05:16:56 PM

they are transistors.
some types are fixed output, some (like the LM317) are variable i.e. adjustable with an external resistor.
you will have to build a small circuit for it,
but the resistor(s) that determine the output voltage can be replaced with pots as you can see here
http://english.cxem.net/power/power63.php

don't forget that it needs at least 2v more than what you want to output (if you want it to behave correctly.)

Gordonjcp · December 23, 2009, 10:24:05 PM

Pots can only carry a fairly low current, unless you buy expensive wirewound ones. Also, for a voltage drop crash you probably only want to drop the voltage a *little* bit - too much and it will just switch off. So what you want to do is calculate the resistors around the pot (in series with the bottom of the track) to set a minimum voltage - basically building an adjustable power supply that goes from (say) 6V to 9V instead of 0V to 9V.

For extra added fun, drive the voltage setting with an oscillator so you're turning the power on and off very quickly - maybe even at audio frequencies. What do you think that might do?

jamiewoody · January 09, 2010, 05:45:37 AM

i found another pitch control! this one takes it to sub-octave levels! talk about a nasty glitchtone!

because it is slowing down the clock speed, it also slows the drums!!!

anymore, i am wiring a switch in series with a pot. this is cool, because with the flip of a switch, i can go to sub-octave oddity!!!