Commodore C64 Restoration

My Repair Journey

My C64 was sitting in a box in the attic for about 35 years. Unloved and ignored. Dirty and probably a lost cause. Along with it, a Commodore 1541 floppy drive, an MPS 803 dot matrix printer, some joysticks, and many floppy disks. I also had the original user guide and the programmer's manual. I am by no means a pack rat/hoarder type, but it always seemed to be a shame to throw away the whole batch.

One day in 2014, I decided to try and resurrect it. I plugged it in, hooked up an old Quasar 13" CRT TV, and turned it on. Nothing. Nada. Just a brief flash on the screen.

So I opened it up and started poking around. I checked voltages. The incoming 5-volt DC was a bit low. I cleaned the DIN power socket with Deoxit, and this helped get the 5 volts back up to spec. I started probing signals with an oscilloscope. Some of the signals were ok, so there were signs of life, but others were missing or had invalid logic levels. Some of the original chips were socketed, so I removed them and cleaned the contacts with Deoxit, also. This helped a little, but some signals were still missing.

There are many, many YouTube videos dedicated to bringing old C64s back from the dead. Some of these demonstrate a shotgun approach, where the YouTubers just keep changing out chips until it works. The problem with the C64 and troubleshooting is that many aspects are non-obvious or misleading. Almost any single chip failure can result in a dead unit. Many of the original MOS Technology (later known as the Commodore Semiconductor Group after a takeover - the Wikipedia link makes for interesting reading) chips exhibited failures due to process issues at their fabrication plant. MOS is best known for developing the 6502 processor chip, which found its way into many early game consoles and most famously, the Apple I & II. They later developed a successor chip, the 6510, used in the C64.

Several YouTubers have reported a widespread failure in the PLA chip, resulting in a black screen. So I ordered a PLA replacement based on the PLA20V8 chips programmed by a guy named Daniël Mantione. These are very cheap and drop into the same socket. No Luck - still had a black screen.

I also got a C64 "Diagnostic/Dead Test" cartridge to see if it could yield any diagnostic clues. Again, no luck. Even the dead test cart requires basic video functionality to display faults.

So my oscilloscope probing continued, and I found that the AEC signal coming from the VIC II chip did not have valid logic levels. It was only rising to about 1 volt, and sometimes nothing at all. The AEC signal is essential since it determines who can access the bus: the CPU or the VIC-II chip. The VIC chip, among its many functions, is responsible for refreshing the C64's dynamic memory.

The VIC II chip is at the heart of the C64's video capability. It is one of the reasons for the success of the computer, selling millions of units at a low price point. It was a very sophisticated chip in its day, providing all the computer's graphics, color capability, and sprites used in gaming. Unfortunately, as mentioned above, the chip suffered from process defects and overheating, leading to many failures.

Knowing that replacement VIC II chips (for NTSC C64s at least) are unobtainium, I started unsoldering and pulling every chip from the board that was connected to the AEC signal, one at a time, checking the signal each time. The theory was that perhaps one of the chips was loading the signal down, so it was worth a shot. I replaced the unsoldered chips with sockets in case some of them had also failed. None of the chips proved to be the culprit, so that left just the VIC II chip.

The "patient" languished on my workbench for many months, and I occasionally checked the web for NTSC VIC II chips. The problem is that even if you find an original VIC II, and even if the seller says "tested", how long might it last? And the prices were crazy because the supply is so limited. In Europe, the NOS PAL versions are more available, but that requires modifying the board and probably a PAL-compatible monitor.

Kawari to the Rescue

I was aware of Randy Rossi's VIC II replacement project that he called "Kawari". Randy spent several years creating and refining a replacement for the VIC-II based on a field programmable gate array (FPGA) design. He reverse-engineered all the functions of the VIC-II chip, which was a daunting task, to say the least. He had some setbacks and chronicled them on his YouTube channel here. He intended to open-source the hardware and firmware and make a small number of completed PC boards available. The biggest setback occurred when the original FPGA supplier went hockey-stick on availability due to supply chain issues, and deliveries became too long. Andy was forced to do a redesign with a different "Trion" FPGA manufactured by Efinix. He eventually released two designs, a "mini" version which had all the functionality of the original VIC chip, and a "large" version with greatly enhanced functions such as HDMI output.

Randy's GitHub repo documents the Kawari and is located here.

He also has a utility program to tweak the Kawari. This runs on the Commodore itself, so it requires a functioning unit before it can be used.

I had been following the availability of Kawari boards for a while and noted that the supplier only had a few left on his eBay store. I dragged my feet, debating whether the potential fix was worth the expense (about $110). Finally, one day, when I looked, the mini version was out of stock. But I checked the seller's Etsy shop, and he had just one left. So I pulled the trigger and ordered it. I probably got the last remaining Kawari mini available for a while, until somebody decides to produce a new batch.

Here is the Kawari Mini installed in place of the VIC II. No modifications needed, assuming the VIC is socketed.

It arrived a few days later, and I popped it into the VIC II socket. Voila!!!! The C64 came alive and displayed the startup screen. This was using the composite video from the C64 (not the RF modulator).

I nearly fell off my chair, since I was expecting additional failures on the main board.

I typed a few Basic lines in, and it ran Basic commands just fine. This meant that the processor, the OS ROM, and the Basic ROM chips all worked, and the Kawari board was perfect.

This was very encouraging. I then popped in the diagnostic cartridge, and it ran almost all the tests without error, including the memory tests. It did flag some errors with the peripheral chips, but I suspected that was due to the absence of loop-back cables on the I/O ports. But basically, I had a breathing C64 after almost 35 years of total neglect.

So I endeavored to keep on with the restoration.

The picture quality of the old 13" Quasar TV is pretty poor, but the video from the C64 was great.

Keyboard

I noticed the keyboard was a bit flaky, so I ripped it apart, removing all the key caps and cleaning all the contacts. This was tedious.

Here is the keyboard disassembled. I pulled all the keycaps and cleaned up the chassis. I used IPA on the contact PCB and then Deoxit.

Pulling the key caps is a little fiddly since the springs can fly all over, but eventually I developed a precision system of covering the whole thing with my free hand to keep the springs from flying away. Haha.

In the end, I managed not to lose any.

I cleaned all the keycaps in mild dish detergent and warm water.

The carbon conductive pads on the key stems were wiped on plain paper to make sure they were clean before re-assembly.

The Power Supply

The original C64 power "brick" is known to be unreliable. The most common failure is for the internal 5-volt regulator to malfunction, resulting in a catastrophic overvoltage to the C64 and potentially damaging multiple chips. Most restorers urge people to get rid of the original supply asap. Building a new supply is not a difficult thing, and I started to plan a mini project for it. I came across a YouTuber who had successfully reused the original supply enclosure and rebuilt it with new components, namely a 9-VAC transformer and a small 5-volt DC switching regulator. I was dubious about salvaging the plastic enclosurebecause it is entirely "potted" with epoxy, but decided to try it anyway, following his video.

After carefully prying off the bottom of the supply, I ran a thin knife around the inside to separate the case from the ugly green potting material. I pulled out the cables for the AC input and the low-voltage output so they could be reused. I snipped the cable leads off, retaining as much length as I could.

Then, using two pieces of wood on either side of the box below the fins, I repeatedly rapped the whole thing on the concrete floor in my workshop. Sure enough, the ugly green block slowly emerged from the enclosure!

Having dealt with encapsulated electronics in the past, I never would have thought this was practical, but it worked. So now I had a usable case for the new supply that was authentic-looking.

More Power Supply Photos

I got this tiny Mean Well 5-volt DC 3-amp switching supply. There is a version without the metal cage, but I like the additional sheilding and heatsinking provided by the metal.

It only measures 2.5x2x1.1 inches, so it should fit in the old enclosure. It only costs $9.00.

I also got this Jameco 9V 1500mA AC adapter. This required liberating it from its case. A little work with a Dremel and it came right out. I removed the AC prongs by heating them with a soldering iron then attached leads. This cost $10.

I epoxied in threaded hex spacers so the bottom can be attached with screws..

I used a surplus blank PC board to make a new bottom. Here is the switching supply mounted on it before drilling holes in the corners for mounting screws.

The bare 9 VAC transformer is epoxied in the case. I also added an inline fuse holder for the primary for safety. I put in a 1-amp fuse.

The finished new power supply is in the original case. It seems to be completely stable and has been running for a few days now. It was a tight fit to get everything inside, but it was worth the effort and will be fine for years to come. I reused the input and output cables. Definitely worth the peace of mind and not having to worry about the old supply destroying the C64.

Just visible are some plastic feet screwed on the bottom, and they stick out a little. These could have been smaller, but that's what the local Ace Hardware store had in stock.

The 1541 Floppy Disk Drive

Another pleasant surprise. I dug the old floppy drive out of the box of Commodore stuff, plugged it into the C64, stuck in a floppy with Zork on it, and - wow - it loaded up and ran. I was fully anticipating having to do surgery on the 1541. (Zork was an old text-based adventure game). Then I tried some other graphical games and utilities, and most ran fine. I believe some of the floppy disks were damaged by heat and cold in my attic after 35 years, but many still worked. It could also be the case that the drive needs a head cleaning and possibly a realignment. I also plugged in an old Epyx Fast Load cartridge (after applying a Deoxit spray to the contacts), and that worked too, significantly speeding up the floppy disk load times.

I have about 50 floppies with C64 software - some may be interesting - next I'll try the joysticks, which were also in the box. I also found a disk with the ancient Geos system on it. This booted and ran. It provides a crude GUI interface with icons, similar to the original Macintosh UI. Kind of cool.

Video Improvements

Orginially, we had a 13" color TV from Montgomery Ward that was used with the C64 - it died long ago and was discarded, but for some forgotten reason, we got a 13" Quasar color TV with a built-in VCR (I think it was for some education project).

I am not so much of a retro purist as to want to get an original Commodore monitor. Working examples go for well over $200, so I am not going there, at least for the time being.

The old Quasar TV has a really bad picture, and I have a less-old 19" HP computer monitor, which is somewhat unused. So I ordered an inexpensive S-Video to VGA converter to connect the monitor to the C64. My version of the C64 features an 8-pin A/V output DIN jack, allowing it to output both S-Video and composite signals. (The older C64s had a 5-pin jack, which only had composite).

S-Video offers a slight improvement over composite, but even more improvements can be made with some simple mods, as described in this YouTube video by Adrian's Digital Basement, which I implemented.

This new combination, using a VGA monitor, provided a much-improved display over the Quasar with just composite input.

Here is Geos V1.2 booted from the floppy disk and running on the VGA monitor. This version used grayscale only - a later version added color. Note that it used 162KB of memory, leaving only 4KB free! I don't know about the math here, since the C64 has only 64 KB of RAM. Haha.

It is amazing how closely this resembles the early Mac OS, which was released on the Macintosh in 1984-ish.

You can double-click icons to open apps and files, as well as drag and drop items on the screen. The interface used layers of pages, each of which could hold multiple icons.

Microsoft released Windows 1.0 in 1985, but it was a dud. They did not gain popularity until Windows 3.0, which was released in 1990, years after this version of Geos.

Software

SInce many of my floppies were not readable, I looked around for another way to get some of the old games and came across this collection called OneLoad64, mostly in cartridge, or CRT, format. There are 1,000s of games in the collection. You can load an SD card with the collection, then play the games with something like the Kung Fu Flash cartridge.