Editing Sinclair QL Troubleshooting Guide (section)

=== Brittle keyboard membrane and flex tails ===

By far the most commonly reported QL fault. The membrane and, in particular, the '''flex cables that feed into J11 and J12''' become brittle with age and develop fracture points that interrupt individual leads. The result is dead keys, dead rows or columns, or a keyboard that works intermittently.<ref name="qlf-kbd">[https://theqlforum.com/viewtopic.php?t=69 "Keyboard membrane repair"], The Sinclair QL Forum.</ref>

This matches the Service Manual's own guidance that apparent major keyboard problems are more commonly the membrane or connectors than the ZX8302 or IPC.<ref name="sm" /> Diagnose the membrane before condemning any chip:

* Reseat and clean both tails at J11/J12 first.
* If the break is close to the connector, the tail can be trimmed back and re-inserted (see the [[Sinclair QL Maintenance Guide]]).
* Replacement QL membranes are still manufactured and are the usual fix for a cracked tail further along its length.