Web Hosting by Netfirms | Free Domain Names by Netfirms

ADD A 3.5 INCH DISC DRIVE, AS DRIVE 'B', TO A PCW.

THE PCW END CONNECTIONS.

THE 3.5 INCH DRIVE END CONNECTIONS.

PARTS REQUIRED:
One 3.5 inch disc drive of the 720K type if you can find one or an older 1.44mb type (do try and steer clear of the very modern 1.44mb drives as there are a number of reports of data errors on discs written too by these drives)
One case to fit the drive and components into.
One 34 pin female ribbon IDC connector. (very common and only costs around 50 pence)
One 26 pin male ribbon IDC connector. (these are now hard to find and cost 4 to 5 pounds)
One 4 pin female disc drive power connector. (very common and only cost a few pence)
One 4 pin male disc drive power connector. (not always easy to find so utilise one from a damaged drive as I do)
One length of 34 way ribbon cable (three feet is about right. Note you will only use 28 of the available 34 strands)
Before we start to assemble our disc drive cable it should be remembered that the ribbon strand with the coloured edge marks PIN 1.
CHECK DRIVE TO SEE IF IT NEEDS 12 VOLTS.
Look at the drive's printed circuit board (around the four pin power connector) as it will normally tell you the voltage requirements and if you are unlucky enough to have a drive that requires 12 volts then you will need to leave two additional strands on the ribbon cable.
Should you have a cased drive complete with it's own power supply then, of course, you will only need a ribbon cable with 26 strands.
The instructions below are for a drive with just the 5 volt requirement --- the norm.
PCW END OF CABLE
Now take the 34 way ribbon cable, remove 6 of the strands from the opposite side to the coloured edge (strand 1 to go to pin 1) and discard them. Using a sharp knife or razor blade slice through the insulation between strands 26 and 27 and then strands 27 and 28 for about 2 to 3 inches. Now fit the 26 pin male IDC connector to the ribbon cable as illustrated above using strands 1 to 26, then solder on the 4 pin male drive power connector -- strand 27 to pin 3 and strand 28 to pin 4 as illustrated-- that finishes the PCW end.
DISC DRIVE END OF CABLE
We now turn our attention to the other end of the ribbon cable, take your sharp cutting tool and slice between strands 6 and 7 down about 2 to 3 inches and then do the same between strands 26 and 27 and 27 and 28. Now fit the 34 pin female IDC connector (but first remove any protruding lugs on the connector, as then, it will not matter which end is designated as pin 1) to the cable, this can be a little tricky as the ribbon cable strands 7 to 26 must go to pins 15 to 34 in the connector and strands 1 to 6 must go to pins 7 to 12 in the connector. To check to see if you have got it right, pins 1 to 6 and pins 13 and 14 in the connector should be unused. Now solder on the 4 pin female drive power connector strand 27 to pin 2 and strand 28 to pin 1.--- that finishes the disc drive end.
ALTERING THE 3.5 INCH DRIVE
If you have an early model 3.5 inch 720K drive (with it's built-in ready signal on pin 34) then this makes for an easy installation and will mean you can use most of your original software, but if not and you want one, then a hunting you must go--car boot sales, junk shops and you might even find one at a Computer fair -- but will it work? -- left in the loft, attic, shed or garage in the cold and unloved for ten years or so, would you? ---- to be honest I find most of them still do.
For a few pounds you can buy from a Computer Fair a second-hand older type 1.44mb drive or a second-hand 720K (later issue) type drive, then all you need to do is to link pins 33 and 34 on the drive and away you go!

The illustration is of a drive that was to hand, most are similar.
Whilst bridging out pins 33 and 34 make a note of which end pin 1 is, so when you can fit the connector you get it the correct way round, first time. Having a ready signal on at all times does mean that you will not be able to use Disckit to format your discs unless you wish to reboot each time (there are plenty of Public Domain Programmes around to do this job) and you will need to have a disc in the drive on Boot Up.
One word of WARNING do make sure that the power connectors are wired correctly and that only 5 volts is present (unless you have an early drive that needs both 5 and 12 volts) -- otherwise BANG goes your drive. If you make an error with the ribbon data connections, no problem, it will just not work.
© J.R.P.King. Return to Help index page.Go to top of page.