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The production of a lead to connect a 3.5 inch external disc drive to an Amstrad CPC6128+ is somewhat complicated by Amstrad's use of a 36 way Amphenol connector, this being identical to a Centronics connector, but using a different numbering system as indicated in the CPC6128+/CPC464+ User Instructions Manual.
A close look at the numbering on the 36 way socket on the back of the CPC6128+ machine does prove, in fact, that Amstrad used a Centronics socket. Therefore for this project we will ignore the user manual, notwithstanding the fact that it is numbered wrong anyway, and work with the numbering on the industrial standard 36 way connector --- the Centronics Plug and Socket.

• PARTS AND TOOLS REQUIRED
• Centronics 36 way Plug (suitable to take a Ribbon Cable)
• 34 way IDC Plug (suitable to take a Ribbon Cable)
• 3 feet of 34 way Ribbon Cable
• Multimeter (not mandatory)
• Side cutters and a sharp knife or Razor blade.

Using a sharp knife or razor blade completely remove wire 34 from the Ribbon cable (opposite side to the blue or red stripe), then clamp the 34 way IDC plug on to the Ribbon cable with the Blue or Red stripe flush to one end. Now clamp the Centronics plug to the Ribbon cable with wire 33 flush to the pins 1/19 end, thereby leaving pins 18,35 and 36 unused. Hopefully when you have finished your lead it should look like the illustration below, you can always take your multimeter and test that the pins not requiring any connections, are in fact unused.

The time is now right to test your handy work, plug the IDC connector into your 3.5 inch 720K drive and the Centronics connector into your CPC6128+ and then plug your external disc drive into the mains voltage and switch on. Now switch on your 6128+, press f1 and load your CP/M Master disc. If it should fail to load and the message Drive A: Disc missing -- Retry, Ignore or Cancel appears you must switch everything off and turn the IDC connector over (you might have to remove the lug(s) from the outside of the plug) . Repeat the aforementioned process and this will tell you, all being well, that you have two drives. Load disckit from your CP/M Master disc and try formatting a disc (must be a 720K not 1.44MB) in drive 'B' (your external 3.5 inch drive) and also try copying data between the two drives -- a reminder -- if you have bodged your 3.5 inch drive by shorting out pins 33 and 34 to obtain a ready signal, then disckit will not function normally after formatting and will tell you that you have a disc in drive 'B' no matter what you do -- just reboot.

Whilst researching data for this help page I came across the following web site http://www.trans-it.de/cordes/cpc/english which contains reference to the Schneider CPC6128. This machine has, like the Amstrad CPC6128+, a Centronics socket for connecting a second drive and the site's Webmaster, Ulrich Cordes, offers a very useful illustration of a DIY lead to connect an external drive -- do note -- this lead will not work with the 6128+.

Footnote Do you know the meaning of IDC, no it is not Internet Data Center but Insulation Displacement Connection (or Contact) -- so now you know.

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