C64 uses a simple keyboard: basic PC board, and the keys have conductive, silicone rubber prongs on the ends, so when you press a key it makes a circuit. The microprocessor scans the 20 keyboard lines in such a way that it can tell when a key is pressed. Certain keys (like the RESTORE key) have their own lines, and the caps lock key does as well. So really it's something like 16 lines plus.
Anyway, the keyboard is not sealed, so dust can get into it; and when that happens, the keys get wonky. Either they don't work, or you have to press hard to get a keystroke, or you get repeats. Fine if you "hunt and peck" or use it for games only; not so good if you touch-type.
This shack has always been dusty and even though I kept the thing covered when not in use, eventually dust got into the keyboard and it started behaving erratically. The first time it happened I had two basic choices. The first was to try to fix it myself; the other was to stop using the computer. The computer was well out of warranty by then.
Three screws hold the case together; once they're out, it opens like a clamshell. Unplug the power LED and the keyboard cable, and the top comes off. Six screws (as I recall) hold the keyboard in; it's a pretty sturdy assembly. Once it's free of the top case you take out approximately fifty thousand tiny little screws and the PC board comes off.
...once you desolder the caps lock key wires, that is.
I did not know how to solder in 1984; I had my friend Eric M. do it. He did a good job; the scars on the thing are from the later times when I repeated this repair, because I was not very good at soldering before about 1990. With the board off I cleaned the prongs and the contact pads on the board with isopropyl alcohol (IPA) and then reassembled...and to my delight, it worked fine.
Later, I broke off the "3" key; and when that happened, I got very lucky. You see, Radio Shack was selling surplus keyboards. Specifically, they were surplus Commodore 16 keyboards. The C16 had used exactly the same shell (different color) as the C64. With the exception of the actual keyboard connector, the keyboard assembly for the C16 was identical to that of the C64. So, I bought one; then either I or Eric desoldered the keyboard cable from the broken C64 keyboard and soldered it into the C16 keyboard. Plugged it in, and it worked perfectly. Perfectly. It was a different color than the original keyboard, but that just made my 64 unique.
Christmas of 1984 I got a printer; and because I'd print out whatever writing I'd done before shutting down, I used both paper and ribbons at a prodigious rate. Well, once Software Etc. opened at the local mall, I could get 1,000 sheet packs of fanfold pinfeed paper for not a lot of money (Radio Shack sold the same thing for 3x the price) but the ribbons, ironically, cost a fuckton.
Then I learned that WD40 has absolutely no deleterious effects on dot matrix printers; and further, that the solvent in it had the effect of rejuvenating printer ribbons. In other words, one could pry off the top of the ribbon housing, hose it down with WD40, let it sit for a little while, and then presto! It's like a brand new ribbon.
Friends later got some kind of Panasonic dot-matrix printer which could do near-letter-quality (NLQ) printing; it did this by printing one row, and then moving the paper about 1/64", and then printing another row. It took twice as long to print but it looked great. Anyway, unlike the Epson's 8" wide ribbon cart, this printer used a little cart that was 3" square, and it rode on the print head carriage. The ribbon itself was thus shorter, and the demands of NLQ printing required a pretty fast ribbon speed. So the ribbon wore out pretty quickly.
This wasn't a problem if you replaced the ribbon when it started to fade; but if you used the WD40 trick? It might last as much as 2.5 times longer, but then one day you'd be printing along and things would be okay, and then GRONK the printhead would stop and the printer would start beeping, because the pins that made the dots would punch through the ribbon and get jammed up in it.
Years before I had a computer I'd bought a small desk at a garage sale. Paid something like $3 or $5 for it. That became my printer stand; I cut a slot in the back of it and put paper on the shelf, so it could feed through there and up to the printer. Worked pretty well.
Around my birthday in 1985, Toys 'R' Us was trying to clear out their stock of Commodore hardware; and among the things on sale was the Commodore VIC-1520 plotter. It was an actual X-Y plotter, not a dot matrix printer; it had four pens (red, green, blue, black) and you could tell the thing to plot text in any of those colors, as well as draw graphs and so forth. I got just enough money from my birthday to buy one, and I used it to plot trajectories and stuff.
Come final exams time, my physics teacher told the class that we could use a single 3x5 piece of paper as a cheat sheet, and anything we could fit on that sheet was fair game. The plotter paper was 5" wide and came as a roll. So you know what I did: I wrote a program that used the smallest-size text, and plotted the majority of the semester's equations on a 3" long strip of plotter paper.
It broke some time later. The tiny nylon gear on one of the motors split. Here's one way to fix it. But even if I got that part working? Even if the pens I have still work? I have two rolls of paper for it. *sigh*
My printer--an Epson RX-80 F/T--blew a tractor feed. The tractor feed is basically a small caterpillar tread, with cone-shaped protrusions on it, spaced to fit the pinfeeds on pinfeed forms. A motor turns a shaft running through a pair of these, spaced distant enough to fit the paper; and this is how the paper is fed into the printer.
To load the printer, you open the pinfeed clamps, lay the paper on them, and close them. But on one side, the spring that held the clamp in the open or closed position came loose. Turned out that a little peg about 1/8" across had broken off, and the plastic was a kind that no commonly available adhesive would touch.
Rubberbands. Several of them. When the other side went, I fixed that one, too, the same way. I tried to find replacement tractor feeds for the printer, but never found them. A couple years later I bought a used laser printer, the Brother Hl8e, which used the Canon SX laser engine. I was, by then, an expert at repairing the Canon SX engine, and I knew where to order all the parts for the things I'd ever need; and so I took this tired old unit and rebuilt its fuser unit (which was the most common failure point for the SX engine) and proceeded to run several more thousand pages through it. Once it blew its AC power supply, but that was a $50 part and it took longer for the part to get to me than it did for me either to diagnose the failure or to replace the part.
The hacks I came up with during those years pale in comparison to the hacks some guys did. A friend of a friend was an Atari guy, and he actually built logic circuits to do things; I never understood digital logic and when I learned how dead frickin' simple 7400-series TTL logic is, I kicked myself. There was a lot of cool stuff I could have been doing, had I known.
But in the basement I have a digital clock I built for my digital logic class. Provide a good 5v supply and a 60 Hz clock and it'll keep time. A bit expensive to build, because each digit is built on its own breadboard, and they're made with counters and 7-segment decoders and-and-and, all of which are pricey chips to buy. But it's made out of nothing but logic gates; there is absolutely no software involved.
Built other projects for school, in fact. A modem--albeit a very simple one. A parallel-port interface for a robot arm. Used a 68HC11 microcontroller as the basis for a simple calculator. I never disassembled a final project; I'd buy a new breadboard instead.
I think the saddest thing about my electronic knowledge is how little of it I actually use. I don't do anything with it; if inspiration were to strike I could build all kinds of neat things--but I never get those kinds of ideas.
It makes me realize that I am very much my father's son; Dad was not a creative type, but when something needed to be built or made, he could do it, quite nicely. He built the partition wall between the kitchen and the family room in the bunker; the only thing wrong with it was the way he taped the corners. (Should have used corner bead, Dad!) This summer I'll have to go up on the roof and rebuild the cupola; he did it last time, about twenty years ago, but it's had it, and needs repair again. I'll reattach the weathervane at the same time, I think.
I'm going to be installing a new fence in the front yard. It's not a complicated thing. And I expect I'm going to need to do something about the pillars on the front porch, too--and they are not complicated, either.
Dad didn't build things just to build them; he never seemed inspired to make things solely because he could--but when something needed making, he could make it. That's not a bad way to be.