Editing Acorn Archimedes A310 (section)

== Decoupling capacitors C37, C38 and C39 ==

Acorn specified three 100 µF 16 V 20% tantalum capacitors, part 0611,101, at C37, C38 and C39 as supply decoupling on the main PCB.<ref name="cl300">Acorn Computers Limited, ''Archimedes 300 Series Service Manual Component Level Supplement'', part number 0476,145, Issue 1, October 1988. Section 5.1 Parts Lists. Hosted on this wiki: [[Archimedes 300 Series Service Manual Component Level Supplement]].</ref> C37 decouples the 12 V line, so a 16 V part sits at only 1.33 times the rail it is decoupling. Tantalums are intolerant of over-voltage and fail short, and these positions are the ones most often found burnt on surviving 300-series boards, typically presenting as a machine that will not start.

If you replace them, a higher-voltage part is a sensible substitution in the C37 position. Check the PSU rails at PL5 (+12 V), PL6 (0 V), PL7 (+5 V) and PL8 (−5 V) before and after.<ref name="sm300" />

The full capacitor list for this board is on the [[Acorn Archimedes A305#Capacitors|A305 page]], from Acorn's component-level parts list.<ref name="cl300" />