Editing Sinclair ZX Spectrum+ Troubleshooting Guide (section)

== ⚠️ Before you start ==

* '''There are no mains voltages inside the computer.''' The Spectrum+ runs from an external 9 V supply; the highest voltage on the board is +12 V. The mains transformer is inside the external PSU brick.
* '''Never plug or unplug anything into the expansion edge connector with the machine switched on.''' This is not a general caution — it is reported as the primary cause of '''80–90 % of Spectrum faults'''. The keyway locating peg on the interface plug drops out with use, allowing the connector to move sideways and short the bus lines together. Because most of the ICs hang off that bus, the damage can be extensive.<ref name="ian" />
* If the keyway peg is missing from an interface, make a replacement: cut the hinge section from an old cassette box, shape a peg from it and glue it in place.<ref name="ian" />
* Hairline solder splatter can measure several ohms and produce very misleading symptoms — inspect visually before chasing anything complicated.<ref name="sm48" />