DIY Microdrive Cable

Recently, since I’ve been using my ZX Microdrives again, I have found that the cable connecting the Microdrive pair to my Sinclair Interface One has become a little unreliable. I have seen second hand cables for sale but I couldn’t be sure they were in a similar state. There is Retro Computer Shack selling new cables via their eBay shop complete but, me being me, I wanted to have a go at making my own. The advantage being, I could make it as long as I required.

I had some ribbon cable in stock. I bought a reel of RS Rainbow 24-Way IDC on eBay ages ago. So the only thing left was to find the connectors. The particular IDC connectors turned out quite hard to find but I persevered and eventually found some on Amazon. They arrived in a reasonable time so I set about making up the cable.

The first step was to remove the pins where the ‘key’ would go. This was as easy as counting three along from one side and pulling the two pins in that position out from the rear of the connector (remove the cable clamp carefully first). Note that this is opposite to the edge connector type that I used for the Microdrive Through Connector¬†Where the pins are removed from the front.

After this, I simply pushed a bit of stripboard in to the resulting gap to make a key and then clamped the connectors to the cable using my bench clamp. Finally I cut the small over-spill of cable off with my Olfa knife.

Making the Microdrive Cable

Making the Microdrive Cable

In this instance, I roughly doubled the length of the cable. Since the most stress happens when you remove or connect the Microdrive units. The extra length of cable slack allows you to push the connectors in or remove them without resorting to pulling on the actual cable. It also ensures that if the Spectrum/Interface One gets moved, the Microdrive cable is not stressed either.

Microdrive Cable In Situ.

Microdrive Cable In Situ.

This was a simple project once the connectors were found but it does depend on having a good clamp or vice to press the cable clamps home properly.

[UPDATE 31st Oct 2017]
Tired of snapping bits of breadboard to make the keys, I looked for an alternative. After much searching I hit upon the idea of using 51mm plastic coated paper clips.

51mm Coated Paper Clips

51mm Coated Paper Clips

I have found a screwdriver of 5mm shaft diameter to be perfect for forming the ‘C’ shape bend in the paper clip material. I push the rounded end into the edge connector to see how long to make the ‘legs’ and then cut them accordingly. I deliberately cut them 1mm or so too long and then compress them into the edge connector with the same vice I used to do the cable. This has the effect of spreading the paper clip material out in the edge connector and making a good friction fit. It seems to have worked, I’ve had no trouble with the cable as yet. The fact that the paper clips are coated means there is less chance of a short-circuit if the key came adrift, although metal only versions would work just as well.

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