Apple II Floppy Drive Cable Retention Clamps

8 Jul

The Apple //e I recently acquired was missing the floppy drive cable retention clamps. As you can see from the manual pages, they retain the cable against accidental pulling, which could possibly break the floppy controller.

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However they also reduce electromagnetic emissions (EMI). The ribbon cable has a copper braid, which I assume runs the length of the cable. It does not terminate on the floppy drive so it would serve no purpose other than EMI shielding, and to reduce coupling between adjacent wires. Nonetheless, the braid ought to be electrically bonded to the chassis, hence the need for the retention clamps.

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I made the clamps out of 1/2″ x 3/32″ brass flat stock available at most hardware stores. It comes in a 12″ length for about $6. Take a sharpie and ruler, and mark off 2″ increments. Draw a centerline down the stock, then mark off 1/4″ from the each 2″ increment; this is where the holes will be drilled. Center punch the holes marks.

Drill 3/32″ holes for the back-plates and 1/8″ holes for the front plates. Tap the 3/32″ holes to 4-40 NC. Saw across the 2″ marks and file the edges smooth. Mark off a notch 1.2″ x 0.1″ on one long edge of each piece, then file the notch.

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The drive cable lug will sandwich between the two pieces, which in turn will be held to the chassis with 4-40 x 1/2″ machine screws.

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