I found an old Commodore 64c without a box, cable, or anything else and I want to put it back to work.

In order to do so, I need to turn it on to see if it works. I've already found the pinout of the power port but I don't know some characteristics of the 9 Vac supply waveform. These unknowns are the frequency, the waveform type and if it stays positive or goes positive and negative. I have the European version.

Does anyone know this information?

  • 2
    I would be astonished if that was anything other than a nominal 9V tap off the mains transformer. So, approximately a 9V RMS sine wave at 49–61Hz.
    – pndc
    Oct 7, 2023 at 16:20
  • With or without the negative edge?
    – jack07Code
    Oct 7, 2023 at 17:14
  • 2
    @jack07Code Well, if it's AC, then it would have negative as well, wouldn't it?
    – Raffzahn
    Oct 7, 2023 at 17:26
  • 1
    @Raffzahn depends on how you define zero and how many pins you have. Floating, one or other side referenced to ground, or even a midpoint referenced to ground are possible. (All of these are used for mains sockets in different scenarios, though floating is rare) Oct 13, 2023 at 15:15
  • @user1937198 Seams you're mixing up the nature of Alternating Current (AC) with voltage measurement. You're right that voltage is a reference based value, but direction of current is not. It's either or. If it does not change (on a regular base) it's DC, otherwise it's AC. That's why an AC system inherently has a mid point. And while AC can be measured as Peak-to-Peak, it rarely is. Nominal voltage for AC is always given as RMS, based on that mid point. (Gedankenexperiment: describe the workings of a diode bridge without changing direction)
    – Raffzahn
    Oct 15, 2023 at 13:36

1 Answer 1


The 9VAC is just 9VAC out of a 9VAC transformer secondary. Sine wave. 50 Hz since you have an european C64.


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