I'd like to thank the following folks who made this possible:
Nak - For his paddle design (though it was a wee bit off)
sch�nberger - for inspiring me to actually wear my C64
tomtiki for giving me correct schematics.
And finally Paul Slocum for making Cynthcart
DISCLAIMER!!! If you are not sure what you are doing ask someone for help. I am not responsible for any damage done to your C64, cherished childhood memories, or person, if you follow some or all of these directions. Be careful with electronics and ALWAYS UNPLUG THEM when working on them.
For this project you will need the following:
A Commodore 64 (any model)
A Soldering Iron
Some wires (color coded is good, though mine is not)
A Cynthcart cartridge (these can often be found on ebay)
2 500k Potentiometers
A guitar strap
2 1/4 inch nuts and bolts
6 Washers (big enough to fit on a 1/4 inch bolt)
Some paint to make your C=BOARD fancy!
Here's a sample MP3: Noise in A
And another 8bit2, this one also features a Korg DS10
Step 1: So, Exactly What Are We Doing?
1. Get Cynthcart
If you just want to make music on your C64 this is the simplest way. Cynthcart is a solid sta6te cartridge that makes your c64 a synthesizer when you boot with it inserted. Most of the controls in Cynthcart can be done with the keyboard, though adding some knobs helps with certain aspects of it. Cynthcart can usually be found on Ebay, I got mine for a little over $20.
2. Paint it
Again, this is optional, but if you are going through all this trouble to mod your c64 you might as well give it a little war paint.
3. Add a strap
Sure, you could just sit it on a table and play it, but to truly rock out you need to WEAR an instrument. Thus the C=BOARD is also a C=TAR.
4. Add 2 control knobs
These knobs will be used by Cynthcart for a few different functions. While most of this can be done just using the keyboard, the knobs give you greater control and easier more analog input.
Step 2: Paint It!
Before disassembly, remember these things: Don't lose your screws, keep something handy to put them in. And always check that you are static free before handling circuitry, Simply touch something grounded once in a while while working.
First, we need to disassemble the c64. Not as hard as it sounds. On the bottom towards the front are three screws. Undoing these and carefully turn it right side up again.
Now you can open the C64, it pivots open like the hood of a car, with the clips at the back working sort of like hinges. Be careful as you do this since the top of the machine and the bottom are still connected by some wires. On the left is a ribbon cable that connects the motherboard to the keyboard. Take note of it's orientation and carefully remove it. Do the same with the small wire on the right that connects the power light to the mother board.
Now remove the screws holding in the mother board and remove it. Then remove the keyboard from the top half of the case. Note that there are a lot of little screws in the keyboard and a few medium sized ones around the edges, you only need to remove the medium screws to get the keyboard out.
So now you have the two halves of the case separate from all the electronics. Next put some masking tape over the c64 logo and the power light and power logo. Make sure that the tape is down real good and cut away excess tape with a sharp hobby knife or razor blade.
Now you may paint it however you want. I used a red krylon spray paint made for plastics for my base but I think other paints should stick to this plastic. I then masked off a racing strike and painted that with white primer.
Step 3: The Strap
I decided to use a standard guitar strap because I had one handy, but other straps could work too. While there are better ways to have done this step there are few easier ways. Feel free to try your own idea, this is just what I did.
I drilled holes in the case, about 1/4 inch I think. I put them in the lower case, about and inch or so from the front. There's room for hardware in that spot and the plastic is fairly thick there. The nut, bolt, washers and strap combination provides some support for the case and a really sturdy connection.
Here's the order of things going on the bolt shaft:
washer, strap, washer2, goes through case into: washer, nut
Think of the washers as the bread in this industrial sandwich.
Step 4: Knobs
Note: If you are afraid to solder on your C64, you can instead make a paddle box that plugs into your joystick port. There's a link in the next step to an Instructable on how to build one.
Basically what we are doing is connecting two 500k potentiometers (pots) to the number one joystick port. They use the paddle circuits to give your synth some analog controls. Now I want to leave the outside of the port unchanged so I can still plug a stick into it can play a good game of Zaxxon, so I have to solder my pots to contact points on the bottom of the motherboard.
The C64 mother board has a thin sheet of metal on the bottom, soldered to the edges, this is the universal ground for the board, between the rest of the board and the sheet is a sheet of insulator (cardstock). You will need to unsolder a few of the contact points for the ground sheet on the right side of the board so that you can bend it back to reveal the bottom of the joystick ports.
Now solder the pots to each other and the board following my handy diagram. Finally, drill some holes in the top of your C64 to put the pots into. There's a lot of open real-estate in the top of a C64 so you have some aesthetic options.
Step 5: ROCK OUT!!!
Here are a few links that may help if you are having trouble.
Pot instructions for MSSIAH
Explanation of the joystick port
Nak's homebrew paddle box instructable(good if you don't want to solder on you C64)
Technical Overview of the Commodore 64