Side Select Switch - Alternative Method

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There are already a couple of procedures for implementing this mod, however in my opinion I think this is the neatest way, particularly if you’re using an enclosure for your 3.5" floppy drive. Instead of cutting up a ribbon cable and soldering wires and switches, or using bits of wire or paper clips on an empty connector, this method involves soldering the switches onto the actual pins of the floppy drive circuit board itself. This results in a more tidy arrangement, especially if the drive is inside an enclosure. Surprised this method hasn’t been covered before, so I hope this helps someone.


I accept no responsibility for any damage caused to your equipment for implementing this mod.

Fundamental Items Required

  • Internal 3.5" PC Floppy Disk Drive
  • 1x Mini SPDT (SPST would also be suitable)
  • Wire (preferably 2 different colours)
  • Heat shrink tubing
  • Soldering Iron and Solder (obviously)
  • Screwdriver


If you haven’t already, remember to solder pins 33 and 34 together in order to enable the Ready signal, otherwise the drive won’t work with the CPC.


The following schematic shows the general idea of how to implement this mod. It is fairly self-explanatory for those already in the know, but it demonstrates a clear and theoretical view of what the objectives are.

1.) Turn floppy drive upside down and unscrew and remove the metal cover to reveal the PCB and a row of 34 pins which come directly from the ribbon connector at the rear.

2.) Locate pins 32 and 31 and solder two lengths of wire to them. Add some heat shrink tubing for tidiness.

3.) Solder the other end of one of the wires to one of the outer pins on the switch and the other wire to the middle pin. Leave the empty pin free as it is not required. Again, use some heat shrink tubing for tidiness.

4.) To test, use CPCDiskXP to copy a .dsk image to one side of a disk and then a different .dsk image to the other side.

5.) Insert disk, select drive B and type cat. You should now see whatever you put on that side of the disk. Flick the switch and type cat once again and now if working correctly you should see whatever you put on the other side. (Remember: Switch open = side A, switch closed = side B).

6.) With the switch working, you can now mount the switch to your enclosure.


  • I intend to add photos to this procedure once I get round to it
  • The floppy drive I've used for this is a Sony MPF920. Other drives my vary slightly