From one ham radio operator to another
The VIC-20 was Commodore’s second 8-bit home computer, being produced after the less popular Pet, but before the vastly more popular C-64. It reportedly sold almost one million units and was marketed as one of the first affordable “family” home computers. As such, even today, it’s not particularly rare or valuable. The reason I purchased it was for the accessories that were being sold with it.
The VIC-20 I’m exploring here was acquired from a shopgoodwill.com auction like many other items I’ve been able to restore. This computer is in beautiful shape. It appears to have been extremely well taken of, kept immaculately clean, and was stored in its original box. Considering its condition and the other items that were with it, I speculate that it may have had only one prior owner and that he purchased it brand new when it was released. I’ve since added it to the VIC Registry.
The included accessories which compelled me to bid on this auction are a Microlog Air-1 amateur radio interface card and a Microlog Airdisk program cartridge. Also included were the original owner’s manuals, cables and even registration cards. The Air-1 interface card is a slightly rarer commodity these days as it was meant for the niche amateur radio market. And as a ham radio operator myself, I intend to both preserve and use it. What it does is allow you to both receive and transmit morse code and RTTY (radio teletype text) digitally by connecting a VIC-20 or C-64 to your radio transceiver. I’ve uploaded a complete set of photos and a scan of the Airdisk manual to archive.org. The Air-1 manual is available on Mike Naberezny’s website.
A series of small repairs
This particular VIC-20 appeared to have been made in late 1982. The previous owner included a spare 6502 CPU as well as two spare 6522 VIA interface controller chips. The yellow wire on the top left of the motherboard is a reset switch the previous owner had added to the user port. Since this VIC-20 was in such wonderful shape, it only needed a few small repairs. As you can see from the photo, the “5” key had broken off. In addition, it sometimes took 10-15 seconds or more for an image to be displayed on the screen after the machine was powered on, and occasionally no image was displayed at all.
Before powering on the computer I had tested the included original power supply and RF display interface cable. I had also cleaned all the connections, switches and DIP sockets with Deoxit and re-seated all the socketed chips. Adjusting the two potentiometers near the 6560 VIC (Video Interface Chip) did improve the quality of the image, but not the startup time.
The next likely culprits were the capacitors near the video outpost circuitry, especially the larger 50 volt orange ones. One of them tested with an ESR of 3.1 ohms…somewhat high, but still within an acceptable range. The second tested with an ESR 14.7 ohms….definitely bad. After replacing both of those worn out capacitors as well as a lower voltage one closer to the VIC chip, there was no longer any picture delay upon system startup!
Reassembly and enjoying a clean keyboard
With all the electrical repairs completed I enjoyed the sight of a clean, functional 40+ year old computer for a few more minutes and then began reassembly. I replaced the RF shielding on the back of the motherboard. I also replaced the messy and slightly dried out thermal compound on the power rectifier with a modern thermal pad.
Since I already had the keyboard disassembled in order to repair the broken key stem I took a moment to clean the circuit board and key pads with deoxit as preventive maintenance. The broken key stem was easily repaired with a conservative dab of super glue and everything fit back together good as new.
Final thoughts
Many times I receive used electronics that are either damaged beyond repair or simply continue to function just as they have since the day they were built. Newer computers tend to made with “planned obsolescence” in mind by the giant multi-national corporations that sell them. On the other hand, many machines from the earlier days of consumer electronics were made with durability and serviceability in mind.
When I’m able to use my limited skills to keep these machines working as they were intended, it’s not only rewarding from a historical preservation and display standpoint, but it also gives me a deep sense of appreciation for the time and effort that the designers, engineers and fabricators of these machines put into them. Very few of the people who have every used these products will have an opportunity to marvel at the intricate layout of a circuit board or the precise mechanical engineering of a keyboard. I feel truly privileged to be able to do so 40+ years later.
Total Restoration Cost $230