Servicing the Sinclair ZX Microdrive

In my experience, the Sinclair Microdrives were fairly reliable when you consider that they were high speed tape based units. However, if performance does start to drop off, in terms of variable formatting performance when cartridges are known to be good ones (they should format to at least 80K), then the read/write head or the drive roller may need cleaning and/or adjusting.

This guide shows pictorially how to do this.

To get into the Microdrive unit, two screws need to be removed which are located on the top of the unit, below the face plate (if fitted).

Remove the face plate before continuing.

If you are lucky, the top plate may not be stuck down too tightly and gentle but consistent pressure on each side in turn may be enough to lift it. Be careful not to bend it as finding replacements is just about impossible now.

If it won't budge, then try to raise an edge slightly, then carefully dribble a very small amount of white spirit under the edge. Alternatively you can spray a small amount of aerosol label remover (but ensure it is white spirit based). This will soften the glue and allow the plate to be lifted away. Wipe the residue and white spirit away immediately as it can attack the plastic on some units.

If the Microdrive to Microdrive joining plate is still fitted to the base, this must be removed by unscrewing the four small screws holding it in place. This will uncover the small latch at the bottom of the front edge which the Microdrive top case clips into.

If you don't remove the joining plate, you may snap the locating lug.

Now remove the two screws on the top of the unit, revealed by lifting off the top plate.

You should now be able to remove the top case of the Microdrive - lift off carefully, again taking care not to bend or snap the locating lug.

Handle the top case of the unit carefully - it will still be attached to the base by two wires running from the controller PCB to the LED at the front of the case. Lay the top case down carefully at the side of the base unit.

You will now have exposed the read/write head, drive roller to its left and the "cartridge inserted" sensor to its right.

It is now easy to clean the head with a cotton bud, or better, a chamois stick moistened with a drop or two of cassette head cleaning head cleaning fluid.

If you don't have any of this, a small bottle and head cleaning bud is available here.

Now use the cotton bud or chamois soaked in head cleaner fluid to clean all the brown oxide residues from the tape drive rubber. Wipe off any head fluid left on the rubber with a dry cotton bud, or similar.

A common problem is for the rubber drive roller to rise up on the metal rotating spindle it is attached to. If it has, this will have been severely hampering performance and probably tangling and snapping the tape.

Push it back down into place after cleaning.

On a well used unit, inconsistent loading and/or the inability for the unit to find the tape catalogue or program, even with a clean head is usually down to actual wear of the drive roller.

The roller may even have a tape sized groove worn into it - see the picture to the right. If this is the case it needs to be replaced - if you can find a spare - I occasionally have them - drop me an email.

If the wear is not too bad, then sometimes pulling off the drive roller and putting it back on the other way around can cure the problem.

When the service is complete, re-assembly is the reverse of the dismantling procedure. Re-attach the decorative top plate with double-sided adhesive tape.


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