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ADDING A 3.5 INCH DRIVE AS DRIVE 'B' TO YOUR CPC OR +3

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DATA CONNECTOR PC PCW CPC +3 PIN NUMBERS 1 n/c 1 34 2 n/c n/c n/c 3 n/c 3 32 4 n/c n/c n/c 5 n/c 5 30 6 n/c n/c n/c 7 1 7 28 8 2 8 27 9 3 9 26 10 4 10 25 11 5 11 24 12 6 12 23 13 n/c 13 22 14 n/c 14 21 15 7 15 20 16 8 16 19 17 9 17 18 18 10 18 17 19 11 19 16 20 12 20 15 21 13 21 14 22 14 22 13 23 15 23 12 24 16 24 11 25 17 25 10 26 18 26 9 27 19 27 8 28 20 28 7 29 21 29 6 30 22 30 5 31 23 31 4 32 24 32 3 33 25 33 2 34 26 34 1

POWER CONNECTOR. PC PCW/CPC/+3 Pin 1 Pin 1 5volts 12volts Pin 2 Pin 2 GND GND Pin 3 Pin 3 GND GND Pin 4 Pin 4 12volts 5volts 4 PIN POWER PLUG (Pin 1 is to the right.) Most if not all 3.5 inch 1.44mb disc drives and all the later 3.5 inch 720K disc drives use only 5 volts, so it would be, after first checking what drive you have, to cut out the 12 volt link. I have found, on the odd occasion, that the 5 and 12 volt pins are linked on the drive's printed circuit board, so if the 12 volt line is not disconnected the drive lights up like a Christmas tree, never to work again. 26 PIN IDC PLUG (SIDE VIEW) 26 PIN IDC PLUG (END VIEW)

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COMMENTS

Disc Drive Types.

Most 3.5 inch 1.44MB disc drives have been found to be unsatisfactory for use as 720K drives and do not have a 'Ready Signal', it will be down to luck if you find a useable one! -- a good test is to format a disc using CP/M's Disckit (whatever version) remove the disc, then press any key to carry on, and if the program then tells you to remove the disc, you will know you have the wrong drive or wrong jumper settings.

Connection Pin Numbers. The CPC6128 manual numbers the 'B'drive edge connector in reverse, I have listed them above correctly but it matters not if it does not work just turn the IDC plug over. The Spectrum +3 manual would seem to be a copy of the CPC6128 manual, in this area, so the same remarks, as above, could apply but the connection numbers shown, are as per the manual.

Disc Drive Case.

You will need to find a case, or make one, to fit your drive into, although, of course, it will work without one.

Data Ribbon Lead.

Your first task is to make a basic data lead to connect the drive to your machine and as this lead is the same as for the adding a 3 inch drive to your machine, this is Help Page 15 (Titled: Adding a 3 inch drive 'B' to the CPC or Plus 3) read this section first. This lead combined with no change of software will only permit the drive to format at 180K but if you want a higher capacity then you will need to decide what P.D. software you are going to use to run your drive, as this will determine what alterations you will be required to make to the lead, if any. Some CPC software will require a SIDE SWITCH to be added to make full use of the 720K disc capacity but there is available software (on ROM) that does not require any modifications. See Help Page 14 (Titled: D.I.Y. Side switch circuit for CPC 3.5 inch drive) for instructions for wiring a side switch.

Power Supply.

Make up a power supply as per the instructions offered on the Help Page 13 (Titled: D.I.Y. Disc drive 5 volt regulator circuit) but if your drive also needs a 12 volt supply then you will have to purchase, in addition, a L7812CV (price around 50 pence) or an equivalent voltage regulator, wiring up is the same as for the 5 volt regulator.