Power Supply for CPC and CPC plus

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Background

The power supply for the CPC464,664 or 6128 is not in the keyboard unit, it is in the monitor or an external television modulator.

Monitor models

  • The GT64 is the "Green Screen" monochrome monitor for the CPC464 and has the 5V power supply for the computer.
  • The GT65 is the "Green Screen" monochrome monitor for the CPC664 or CPC6128 and has the 5V power supply for the computer and 12V power supply for the disc drive.
  • The MM14 is the "Grey Scale" monochrome monitor for the CPC464+ and CPC6128+ and has the 5V power supply for the computer and disc drive.
  • The CTM640 is the colour monitor for the CPC464 and has the 5V power supply for the computer.
  • The CTM644 is the colour monitor for the CPC664 or CPC6128 and has the 5V power supply for the computer and 12V power supply for the disc drive.
  • The CM14 is the color monitor for the CPC464+ and CPC6128+ and has the 5V power supply for the computer and disc drive.

TV Modulator models

  • MP-1 is the television modulator for the CPC464 and has the 5V power supply for the computer
  • MP-2 is the television modulator for the CPC664 and CPC6128 and has the 5V power supply for the computer and 12V power supply for the disc drive.

Power requirements

The power requirements are (information taken from the underneath of the keyboard unit from real machines):

  • CPC464: computer and internal cassette player: 5V DC @ 2A
  • CPC664:
computer: 5V DC @ 1.7A
internal disc drive: 12V DC @ 0.4A
  • CPC6128:
computer: 5V DC @ 1.7A
internal disc drive: 12V DC @ 0.4A
  • CPC464+: computer and internal cassette player: 5V DC @ 2.4A
  • CPC6128+: computer and internal disc drive: 5V DC @ 2.4A


All voltages MUST be smooth, the CPC does not have an internal regulator!

Power connectors

To connect a power supply to CPC you need the following connectors:

  • CPC classic:
  * 5.5mm/2.1mm power line plug (providing the 5V for the CPC)
  * 5.5mm/2.1mm power line socket (providing the 12V for the floppy)
  • CPC+:
  * 5.5mm/2.5mm power line plug (providing the 5V for CPC and floppy)

Cpc power plug socket.jpg

  • Outer diameter (A) is 5.5mm for all plugs and sockets, inner diameter (B) is 2.1mm for classic CPCs and 2.5mm for Plus
  • short and long plugs exist, the ones used for the CPC and Plus are the short ones with approx. 9.5mm (C)


Pinouts for Power Sockets:

The +5V socket on the back of the CPC / Plus is wired as CENTRE POSITIVE, i.e. the central pin of the plug is +5V and the outer barrel is Negative (GND).

Image:centrepositive.png

The +12V plug on the end of the wire dangling out of the back of the CPC 6128 is wired CENTRE NEGATIVE, i.e. the central pin of the plug is Negative (GND) while the outer barrel is +12V.

Image:centrenegative.png

Using a PC power supply

It is possible to use a PC power supply, however PC PSUs can be dangerous as they easily can pump out 25A or more on the 5V rail - one accidental short in the system and it fries the traces of the computers PCB.

There are ATX breakout boards available on e.g. Ebay or Amazon, which will add fuses to the 12V and 5V lanes of the power supply, so they can be safely used with the CPC and Plus. To avoid any harm to the computer, the 5V fuse should be 4A, the 12V fuse 1A.

Atx-breakout-psu.jpg