Editing Acorn Archimedes A3020 Maintenance Guide (section)

== Power supply checks ==

The on-board PSU delivers +5 V (logic, floppy and hard disc) and +12 V (the hard disc and video-connector pin 12).<ref name="sm" /> Acorn's "action if PSU fails" routine is the safe way to diagnose a power problem:

# Switch off and unplug the mains lead.
# Check the '''5 A fuse in the mains plug'''. If a replacement blows on switch-on, the supply is faulty.
# Check the internal fuse '''FS1'''.
# Confirm the drive-power links '''LK1''' and '''LK2''' are fitted.
# If the supply runs then cuts out, suspect thermal shutdown — check ventilation and the load; repeated shutdowns mean a faulty supply.

Because the PSU is part of the main board, a PSU-section repair is a board-level electronics job carried out with the mains lead disconnected and the primary bulk capacitor discharged — see the [[Acorn Archimedes A3020 Capacitor Guide]].