I’ve seen numerous people, including vintage computer enthusiasts on Youtube, find burn marks on a Commodore 64 and get confused by them. What causes these burn marks, and why are they more prevalent on Commodore computers than Apple or IBM? The answer is simple and it’s not that Commodore owners smoked a lot more than owners of other makes.
Burn marks on old computers come from how they were stored
Burn marks on Commodore 64s and any other old computer or game console happen because of how they were stored. It happens on machines made of plastic, which is why you don’t see burn marks on, say, an IBM PC case. But I know it happens because I’ve done this myself. I burned a couple of my 64s this way.
Burn marks happen from storing the computer and its cables together, with the cable touching the computer.
Computer cables are soft and flexible, while the cases are hard plastic. The softeners that keep the cables flexible will, over time, leech out onto whatever they’re touching. If they’re touching hard plastic, this will slowly soften the plastic. The softening plus the weight of the cable can very gradually cause the cable to sink into the harder plastic, leaving a depressed area where the cable sunk in, and raised areas on either side of the cable from the displaced material.
It’s a chemical burn. That’s why you have something that looks like someone set their soldering iron on it, but the color remained uniform, with no charring.
Preventing burn marks on old plastics
Wrapping the cables around your computer is tempting because it keeps them together, but if you leave it that way for very long, you’ll damage the computer. And the same goes for game console controllers. Don’t wrap the cable around the controller. Wrap the cable onto itself.
I can’t tell you exactly how long this process takes. I can tell you that I put some C-64s into storage sometime around 2010 or so. They were stored in my basement, which protected them from any temperature extremes. I unpacked them sometime in 2018. And when I did, the two machines that had cables placed on top of them had burn marks. The one that didn’t looked the same as it did when I packed it away.
So I know eight years is too long. I can’t comment on less than that. But I also know when we pack things away, we might not know exactly how long it’ll be before we get them back out again. I didn’t think it would take me eight years to get back to my 64s, but it did.
Fixing burn marks on Commodore 64s
There’s no perfect fix for burn marks on Commodore 64s, but you can make it look better. The lack of charring helps. It means you only have raised areas and a depression to deal with, probably no discoloration. Or at least, no discoloration that can’t be fixed with a little sunlight.
To fix it, run a sharp blade along the raised area to shave it down level with the undamaged parts of the case. Then repeat on the other side. The raised area makes the depression much more noticeable. Once you shave away the ridges around the damage, the damage is harder to see.
The sunken area presents more of a challenge. You could fill it in, say, with auto body putty, but you would have to paint the case if you do. If you have bits of plastic from other Commodore gear, say, cut-off broken case standoffs that you’ve replaced with Jeff Birt’s case saver, you could try an old modeler’s trick. You can dissolve some of the scrap plastic with acetone until it goes soft like putty, then press some into the sunken area. However, once the acetone evaporates and the plastic rehardens, it’s hard to ensure color consistency. The acetone may change the color.
I find it best to leave the battle scars as-is. But if you have several damaged cases to experiment on, you may wish to try it.