Editing Acorn Archimedes A3000 Maintenance Guide (section)

== ⚠️ The CMOS battery: check it first ==

The A3000 keeps its configuration and clock in battery-backed CMOS RAM. The backup cell sits at the '''bottom-left corner''' of the board. Aged cells leak, and the electrolyte corrodes the nearby tracks and the bottom-left corner of the PCB &mdash; on at least one documented A3000 this corrosion was the reason the machine no longer worked.<ref name="chris" />

* Inspect the bottom-left corner for green/white corrosion or a crusty residue around the battery.
* If the battery has leaked, neutralise the residue, clean the area with isopropyl alcohol, check the affected tracks for continuity, and repair any broken tracks before refitting power.
* Replace the cell pre-emptively on any machine that still has its original battery. Loss of configuration, a wrong clock, or boot problems are the usual symptoms of a flat or removed cell.