• Mike Brixius

Commodore 64 Power Supplies

Updated: Jul 19, 2021

The original Commodore 64 power supplies left a lot to be desired. While the circuit is a fairly straight forward linear design, one component, the voltage regulator, tends to fail in an unsafe manner. This, combined with the decision to fill the power supply housing with epoxy (called potting), makes these devices potentially dangerous to your Commodore 64 with no reasonable way to service or repair them.

Epoxy potting inside a Commodore 64 power supply
C64 PSU Epoxy Potting

The power supplies tend to fail in 3 ways:

  • The caps fail and allow excess ripple. The C64 becomes unreliable or fails to start but is undamaged

  • The regulator opens and no 5V is output so the C64 will not start but is undamaged

  • The regulator shorts allowing up to 11V through to the C64s chips causing them to fail

This diagram shows how the power port and cable pins are numbered.
Power port and cable pins

If you just want a working power supply, there are many options online. I recommend ones sold by Ray Carlson.

If you want to make your own, then you will need to provide 2 voltages.

1. 5V DC at 1.5A

2. 9V AC at 1.0A

In the video, I use a Mean Well RS-15-5 that outputs 5V DC at 3 Amps and a 9V AC wall wart. This is sufficient for a Commodore 64, but you might consider going with higher specifications if you also want to use the power supply with the Commodore 128.

A Homemade replacement power supply for the Commodore 64 computer
A DiY C64 Power Supply

You can use the pin connection cheat sheet above for your own project. It makes it easier to get the connections right. You will note that the DIN connector shown only has the needed pins. If your connector has all 7 pins then you still only need to connect the 4 shown.

In the future I am planning a more advanced power supply build but, in the meantime, this should get things rolling!

If you have any questions you can add them to the video comments or use the contact form on this website.

You can find the Mean Well RS-15-5 on Amazon

I am currently working on a Universal Bench Supply for Commodore computers that required an external power brick. A related blog post can be found here.

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