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Thread: Pin Out for Power Supply Commodore 64 ?

  1. #1

    Default Pin Out for Power Supply Commodore 64 ?

    The pin out for my Commodore 64 Power Supply shows 2 = GND, 5 = +5V, 6,7 = +9V. When I put my meter probes on 2 and 5, it shows 5 Volts. However on pins 2 and 6, as well as 2 and 7, it shows 0 V. What happened to the +9 Volts? The Power Supply seems to work fine and shows games (e.g "Star Post" ) in good color and sound???

    Thanks for any insight. (I'm trying to determine if a separate Power Supply has failed and should be thrown out.)

  2. #2
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    Pins 6 and 7 are 9VAC. Try putting your DMM on its AC, not DC setting.

  3. #3

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    Also, if you need a replacement PSU, the 9V AC line is only used to feed the cassette and user ports, nothing inside the C64 uses it. So for most uses (with a disk drive or SDIEC adapter), you only need the +5V DC and GND connected.

  4. #4

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    Quote Originally Posted by Kakemoms View Post
    Also, if you need a replacement PSU, the 9V AC line is only used to feed the cassette and user ports, nothing inside the C64 uses it. So for most uses (with a disk drive or SDIEC adapter), you only need the +5V DC and GND connected.
    This is very wrong. 9VAC is also rectified and it is regulated to +12V DC on the classic breadbins to feed VIC-II and SID analog power supplies, then this 12V is also fed to a 7805 that in turn supplies the digital VCC of both VIC-II and SID. The newer C64C boards regulate the SID analog supply to +9VDC needed for the 8580 variety of SIDs.

    Frank IZ8DWF

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