Editing Sinclair QL Microdrive Troubleshooting Guide (section)

== Cartridges ==

Cartridges are consumable and are usually in worse condition than the drives. A drive that fails every cartridge may be faulty; a cartridge that fails in a known-good drive is simply worn out.

=== The felt pressure pad ===

Inside each cartridge, a small '''felt pad''' presses the tape against the head. Over decades this felt hardens, compresses or falls off — its adhesive perishes — and the result is weak or intermittent read signal, exactly mimicking a worn head or weak head springs.

'''Re-felting''' is the community repair: open the cartridge, remove the old pad and its residue, and fit a new pad of equivalent thickness and softness, using a small amount of a suitable adhesive. Work carefully — the tape loop must not be creased, twisted or contaminated, and the pad must sit square so it presses the tape evenly across the head.

Signs that point to the pad rather than the drive:

* The same cartridge reads poorly in more than one known-good drive.
* Read level (measured with the signal test program) is low for this cartridge but normal for others.
* The cartridge reads better if gently pressed while running — a sign the tape is not being held firmly to the head.

=== Tape condition and handling ===

* Tape that has become sticky, shed oxide, or been stored in a hot or damp place should not be run — it will contaminate the head.
* A '''jammed tape''' or '''tight cartridge tape''' is listed by Sinclair as a mechanical fault requiring attention to the clamp spring, rollers and motor.<ref name="sm" />
* Listen when a cartridge is inserted: '''clicking or crunching sounds indicate a weak clamp spring'''.<ref name="sm" />
* Damaged cartridges and "microdrive incompatibility" are treated together in the manual with tight tape, noisy operation and format failures — all point at the mechanics rather than the electronics.<ref name="sm" />
* Check the '''write-protect tab''' before assuming a fault: a protected cartridge cannot be written or formatted.<ref name="sm" />