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The VIC-II and SID chips in the C64/128 are prone to over-heating and are rather expensive to replace nowadays. Some other ICs in these machines may have the same issue.

An unmodified machine includes a large metal RF shield which usually performs the duty of being a heat sink for VIC-II, SID, and other chips. However, the RF shield is frequently missing from machines that have been damaged, worked on, modified, refurbished, etc. Therefore, that heat sink is also gone. I also question whether it was ever a very good heat sink to begin with, or just another way for Commodore to control costs.

What is a reliable modern replacement for the original RF shield's heat dissipation function? Which chips in the C64 and C128 should have such a heat sink installed?

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Modern heat sinks

I assume this is about heat spreaders, as that is what they do.

What is a reliable modern replacement

Any one available at the usual stores will do it

Which chips in the C64 and C128 should have such a heat sink installed?

All may benefit, as they are NMOS and thus heating.


Background

It's about the surface size - larger surface to radiate the heat results in cooler chip temperature. In reality a plate with fins placed in the middle of an IC will get the most. Already a small one does make a noticeable difference.

The metal used should provide a good thermal conduction like:

  • Diamond (1000 Watt per Meter per Kelvin))
  • Copper (400)
  • Aluminium (250)
  • Iron (100)

As it's about getting the heat from chips to radiating fins.

A darkened surface increases radiation. Although the darkening matter should as thin as possible - at least between chip and carrier, as it's an additional barrier reducing thermal transfer.

Important

Anything surface temperature (without heat spreader) less than 20 degree Kelvin above environment is not worth the effort.

Maximum-Hack:

Dig thru your parts box and see if you can find some old 386 / 486 / chipset heat spreaders with fan. They are still small enough to fit inside a C64 and will get everything way down.

Similar modern RAM heat spreaders can be used across several chips (like the RAM).

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An unmodified machine includes a large metal RF shield which usually performs the duty of being a heat sink for VIC-II, SID, and other chips.

I've worked on dozens of C64s, and have only seen the metal heat spreader/RF shield used in later C64 models, for example the 64C. Earlier "breadbin" models had a foil-covered cardboard RF shield that effectively held in heat, rather than to distribute it. However, these models did have the VIC-II inside a metal box with a heat spreader.

If you have a model with the metal heat spreader, that should provide sufficient heatsinking of the chips which tend to run warm. I'd suggest replacing the thermal paste, as it's probably dried out after all this time.

What is a reliable modern replacement for the original RF shield's heat dissipation function?

I find that 14x14x6mm aluminum heatsinks work well, attached using thermal double sided adhesive tape. I typically put 2-3 of these on the larger chips, depending on how hot they run.

Which chips in the C64 and C128 should have such a heat sink installed?

You can determine this by removing the case and letting the computer warm up for 10-20 minutes. Carefully check the temperature of each chip using your fingertip. If it feels hot, put a heatsink on it.

On an earlier model C64, I'd suggest heatsinking the following chips: CPU, SID, PLA, VIC-II (if it doesn't have the metal box/heat spreader), the 3 ROMs, and both CIA chips.

I'm not as familiar with the later "short board" 64C or 128, so I'll let someone else answer that part.

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  • Spray duster can also be used to help identify hot-spots. Invert the can and spray it over the board. It'll come out as a liquid and as it evaporates it'll leave a very thin layer of frost over everything. The frost will quickly disappear with the hottest locations disappearing first. I've used this without issue on powered-up boards but I wouldn't go overboard with how much you spray on. NOTE: Be careful not to get any of the liquid on your skin since it can cause frostbite. Aug 13 at 3:46

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