Editing Sinclair ZX Spectrum+ Troubleshooting Guide (section)

== Power supply faults ==

The external PSU is a common failure point, and it is repairable:<ref name="ian" />

* The usual fault is the wire snapping or going intermittent '''in the moulded plug or where the lead leaves the case'''.
* To fix the plug end, fit a replacement 2.1 mm plug with '''negative to the centre''' (the traced wire), then fill the plastic cover with silicone rubber before screwing it up — this prevents internal shorts and takes strain off the solder joints.
* At the PSU end, split the case, cut off the faulty section, tie a double knot about three inches down the cable, slide protective sleeving on, and resolder. The knot inside the case stops the joints being strained.
* A bare wire shorting the output blows the '''thermal fuse''' and/or takes out the '''1N4007 rectifiers'''. The thermal fusible link can be replaced by spot-soldering a '''160 mA slow-blow 20 mm fuse''' across the old device. A faulty transformer, however, means the unit is scrap.

'''Intermittent crashes or resets, especially when the machine is moved''', are usually the power plug or the power socket. Replace the socket — do not try to tighten it.<ref name="ian" />