domingo, 26 de marzo de 2017

Story of a Commodore 64

Almost any object can become part of a certain story. This is the story of an old Commodore 64 (8 bits computer) I got for a few dollars here in Buenos Aires. The computers was not working so this is the story of how I found the parts needed to take it back to life.

In part of my spare time I enjoy working on electronics and with nowadays is called “maker culture” and more particularly with retro-computing.
When I was a kid my first computer was a Radio Shack Color Computer II (known as coco 2). I was lucky to get that computer. At that time it gave me lot of fun and excitement. Coco was just great. Still I keep that coco with me, and is working just fine as in the old days. Of course today, it is mostly useless as you can not search the web, or even use a fancy spreadsheet.
I remember Linus Torvalds’ opinion on 8 bit computers: At those days if you had enough documentation and curiosity you could develop a good knowledge about how a computer works. Because computers were simpler than the ones that came after. That is part of the success of a computer like Raspberry Pi.
I think we can still learn a lot of those old computers. It’s just like going to a museum, but a particular one where you can play around
with objects.
Some months ago I got a Commodore 64 for a few argentine pesos. The reason why? The computer did not work. The outside was good, keyboard looked fine, case was in good shape too, but there was no video output and the power supply had been lost. No video, no power supply.
I wondered if I should have removed the pcb and put a raspberry Pi in it, but I decided first to try to repair the commodore and to get or build a power supply.

The cause of the video failure (no video at all/black screen) was the MOS-8701 chip. The chip had to be replaced, and finding one of them nowadays is not easy.
Fortunately, I was able to find a new one. The price was not cheap, but at that point I was committed to get the C64 repaired.

Then, I went to a the house of a friend of mine who owns a c64 and tested mine. With the new 8701 it was working.
Now it was necessary to get or build a power supply. C64 original PSU it was its weakest part. The power supply used to get very hot, and I mean very hot. It was placed inside a dust proof case and that contributed to the increasing heat.
So building a modern power supply using a switching psu would be fine. With parts I have lying around the house: a case, a switching 5 Vdc power supply and a transformer for 9 Vac. Finding a DIN plug the C64 uses for PSU was not easy nowadays. I almost gave up, but finally I could get one. Otherwise I would have had to order it abroad.
I put those parts inside the case, added a 2A fuse for the 9 Vac output. Tested the voltages and the DIN pinout twice, and then plugged into the C64.
The computer is working as in the old days. Now is time to get some games and show the kids how we had fun time ago.

In this video C64 and it "brand new" psu can be seen working:


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