Post Index:

Entries in retro (1)


Refurbishing a Commodore 64

I recently was able to acquire a nice piece of my childhood, namely a 1983 "breadbox" Commodore 64. I used to have one as a kid. It was the very first computer I ever touched, and was basically responsible for getting me into the IT field and programming in the first place. Then my Mom gave it and all our games away to a friend while we were at summer camp, thinking we wouldn't mind since by then we were all up into Super Nintendo and such. Having the highest number of sales (and a 40% market share) of any single model home computer of all time you would think they would be a piece of cake to find. They seem to always be kicking around EBay, but the last one I bid on ended up going for WAY over what I was willing to spend. I think it was around $350 for the main unit and a tape drive, no cables. Ouch.

Last week, I got lucky. An internet forum acquaintance had a VIC-1541 disk drive kicking around in his attic. He offered it up if I was interested, so I had it shipped. I then started poking around EBay again, and ended up winning this unit for just over $12, condition unknown. There seem to be a lot of "parts" C64s on the market, so I wasn't expecting much. Boy did I get lucky. A few more good bids later, and I'm in business.

First thing first: I needed a power supply. The C64 uses a 7-pin DIN connector to provide both +5VDC and 9VAC to the mainboard. I guess the original power supplies were notorious for the regulators burning out, and taking chips with them. Since this fact troubled me (and was basically moot since I had no cables), I looked up the pinout and built my own. A trip to Fry's netted an 8-pin DIN for about $0.59, and the center pin was easily removed with a bit of violence. I had plenty of decently beefy 5VDC wall warts lying around, and DigiKey had a 9VAC one for about $7 after shipping. A bit of heat shrink and some soldering, and I was ready to test the unit out. To connect to the one TV I had with a standard antenna A/V connection, I used the same setup I usually run my Nintendo on. Cross fingers, throw switch.

'Tis the perfect amount of bytes. This means the RAM is most likely still good, so yay on that front!

Trying the keyboard out, I noted many of the keys didn't work most of the time, and when they did there was terrible debounce. So in I want with the screwdriver to see what I could do! I met with a dire warning from beyond time:

Oh man, there goes my 30 year old warranty...

They keyboard is just a bunch of simple conductive pads, similar to a TV remote. A bit of a scrub with a pencil eraser and some alcohol and they shined right up.

Popping the unit back together, I gave it a go with some quick BASIC commands. Flawless!

Next I was dying to test out the SID, Commodores legendary audio chip. These things are crazy hard to find these days. Folks use them in synths and other audio devices, and the demo scene is still going after all these years. Unfortunately, they burn out rather easily. Since there's no real way to make more of these babys every burned out chip is another chip less to go 'round. I found a nice 1 line BASIC audio demo and typed it in. Nothing. Damnit. Luck for me a batch of 10 happened to be found on a warehouse shelf, never before placed into any unit, and tested by the seller. I picked up two.

While I wait for a replacement SID, I decided to clean up the entire unit (full of dust bunnies) and see what I could do to extend the life of the other chips.

So far all I have done was verify voltages with a multimeter, re-check the SID output with a scope just in case it was my TV or something, and added some old heat sinks I had lying around to try to keep this old stuff cooler.

I plan to salvage or fabricate a few more heatsinks for the ROM, RAM, and kernal chips. I would like to make an s-video cable to clear up that picture a bit. I have also begun to work on an Arduino/Rasperry Pi solution to emulate the 1541 disk drive I have, but allow me to read in images off USB or an SD card. More on that to come. Right now I am pretty stoked to be at this point.