Revision as of 11:28, 24 May 2009

Using a Sinclair ZX Spectrum +3 Power Supply to run an Amstrad CPC 6128

If you have made up a SCART cable to use a TV with your CPC 6128, then you'll need some alternative way of powering the machine. The MP2 modulator is the best option, but these are quite scarce and often fetch fairly high prices on eBay.

The power supply for the Sinclair ZX Spectrum +3 is perfect for powering an Amstrad CPC 6128, and these can be picked up on eBay very cheaply.

These provide +12V at 0.7A and +5V at 2A - plenty for the CPC. They also give a -12V line, which we don't need, so be careful not to connect it.

Note that the power supply for the Spectrum +2A model gives the right voltages, but only provides 12V at 0.2A, which may not be quite enough for the 6128.

What You Need:

• A Sinclair ZX Spectrum +3 Power Supply unit (obviously)
• A 6-pin DIN Line Socket - (http://www.cpc.co.uk/ Order Code CN00069 is suitable)
• Either:  A 2.1mm DC Power Line Socket (http://www.cpc.co.uk/ Order Code AR70635 is suitable), and a 2.1mm DC Power Plug (http://www.cpc.co.uk/ Order Code AR70631 (pk10) is suitable), and two short lengths of twin wire.
  
• Or:  A 2.1mm DC Power Extension Cable, e.g. http://www.cpc.co.uk/ Order Code PW01903, which you simply cut in half.
  

Pinouts for +3 PSU:

The pinouts for the +3 (and +2A) power supply are shown below.

This diagram shows what the end of the power supply lead looks like, so this will be equivalent to looking at the Solder side of your 6-pin DIN Socket.

Note that the outer metal cylinder of the DIN plug is also grounded, so take care not to short this to any of the pins or you will blow a fuse inside the power supply.

Pinouts for CPC 6128 Power Sockets:

The +5V socket on the back of the CPC 6128 is wired as CENTRE POSITIVE, i.e. the central pin of the plug is +5V and the outer barrel is Negative (GND).

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

How to Wire it Up:

BEWARE - As mentioned above, the +12V and +5V connectors are wired with OPPOSITE POLARITIES! Please take great care to make sure you wire them up correctly.

The wiring is pretty obvious, really!

Connect the outer barrel contact of the 2.1mm Line Socket to either or both of the +12V pins of the 6-pin DIN Line Socket.

Connect the centre pin contact of the 2.1mm Plug to either or both of the +5V pins of the 6-pin DIN Line Socket.

Twist the wires from the outer barrel of the 2.1mm Plug and the centre pin of the 2.1mm Line Socket together, and connect them to the central GND pin of the 6-pin DIN Line Socket.

It is quite safe to join both of the +5V pins together, and both of the +12V pins together, but DO NOT CONNECT ANYTHING TO THE -12V PIN.

If you have a voltmeter or multimeter, after making your cable up, don't try to connect it to the computer straight away. Plug the PSU into the mains, and check you have the correct voltages and polarities on the two DC power connectors.

If you haven't got a suitable meter, you'll just have to make absolutely certain you've wired it up correctly. If you get it wrong, you may blow the fuse(s) in the PSU, or you might even destroy your Amstrad (though this is unlikely).

Please note that the information in this article is provided in good faith, but I take no responsibility for any errors. Use this information at your own risk.