SCA/Locomotive 3.5 inch Disc Drives

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SCA / LOCOMOTIVE 3.5 INCH DISC DRIVES -- FAULTY ADAPTORS.

One of the following adaptors (or something similar) is fitted to the 3.5 inch 720K disc drives as supplied by SCA for drive units that were offered for sale by Locomotive Software of Dorking. Do note that neither Locomotive Software of Dorkimg or SCA are trading.
It has been found of late that these adaptors have been failing in droves and not enabling the machines to boot up.
To rectify this problem -- only one part is required, a 34 pin IDC female connector, plus a little electronical skill to get your machine running. Remove the adaptor and discard, then swap over the two power leads **** power plug --- push the tiny metal locking tab down in the plug and then pull the wire out, lift the locking tab up and then slide back into the required plug hole -- the PCW 3 inch disc drive uses the 5 and 12 volt connections the opposite way round to the 3.5 inch drive drive.
Next remove the 26 pin IDC plug from the ribbon cable. Then take a sharp cutting tool and slice between strands 6 and 7 on the Ribbon cable either side of where the fresh connector needs to be fitted for about 2 to 3 inches, strand 1 is indicated by the Red or Blue stripe down the edge of the ribbon cable.
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.

If your machine is fitted with two drives (normally your old 3 inch drive is now used as drive 'B') then the new 3.5 inch drive could be fitted with an electronically switchable adaptor that permits booting from either disc drive. The adaptor will be marked as such (see picture to the right) and these are also known to become defective.

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