Why did I buy a Commodore VIC-20?
I started programming as a child with the Commodore 64 that we had in the family, later replaced with the more modern and high-performance (for the time) Commodore 128. I recently came across my old Commodore 128 and... it flashed in my mind. idea of creating a small collection of retrocomputers.
I then sifted through the various used goods sales websites and started buying some old computers. Among the ads was this Commodore VIC-20.
Although the price the seller was asking for wasn't exactly cheap, I still opted to buy. The computer was in fact well maintained and also equipped with its accessories: power supply, joystick, cassette recorder and several cassettes with video games.
Commodore VIC-20, history and specifications
The Commodore VIC-20 has been manufactured by Commodore Business Machines Inc (CBM) since the late 1980s. Being, for the time, a fairly cheap computer, several were sold (about 2,500,000).
It is a color computer, equipped with an 8-bit MOS 6502 processor and 5 KB of static RAM memory. Only 3583 bytes of RAM are free for programs, so apps, as we call them today, tend to be pretty basic. An expansion port is available to increase the amount of RAM or for ROMs containing apps or games that need more than 3.5 KB of RAM.
Commodore VIC-20, restoration
Buying a 40-year-old computer also means having to carry out a restoration. The computer was already working, so the restoration was quite simple.
After disassembling the case and separated all the components, I washed the container well with degreaser and cleaned the keyboard well.
The motherboard was quite dust-dirty, so I thoroughly cleaned and deoxidated contacts by appropriate spray.
I replaced all capacitors, also adding a capacitor that was not present on the motherboard. Evidently, to save on components, some capacitors were not installed (I found the same situation on other Commodore computers). Electrolytic capacitors function as a filter of the supply voltage and, unfortunately, have a defect: the liquid electrolyte present inside, tends to evaporate over the years. That is why electrolytic capacitors must still be replaced on vintage electronic cards. Some capacitors on the motherboard, in fact, had out-of-tolerance capabilities and leaks.
Other types of capacitor and other components do not suffer from aging, as is the case with electrolytic capacitors, so they should only be replaced if damaged.
To complete the restoration, I also added two transil, which serve to protect the board from voltage transients, polarity reversal and surges.
Commodore VIC-20, the test
The final test gave good results. The computer is very beautiful and working in all its details.
To load the games you can use the Datassette C2N recorder and load the vintage cassettes.
Today there is also a floppy disc emulator, which allows you to upload hundreds of games saved via a PC to a MicroSD card. The emulator is called SD2IEC, which connects to the serial port of the floppy disc and takes power from the datassette port. Emulation occurs only on the serial floppy disc and the loading of games is also quite fast.
There are also dating emulators, but these are slower, as the cassette player communication protocol provides for a transfer to 300 bauds, which corresponds to less than 50 bytes per second!
I wrote about the emulator in this article.
Documentation
In support of this article, I also attach the Commodore VIC-20 Technical Manualand Commodore Datassette C2N Service Manual.
They are technical manuals that help you understand the operation of the circuits and can be convenient to carry out repairs.