Editing Acorn A4 Capacitor Guide (section)

== Procedure ==

# Remove the main board. Every other part of the base has to come out first; follow [[Acorn A4 Maintenance Guide#Opening the A4]].
# Photograph the board and record the value and polarity of each part before removing it.
# Remove the old capacitors with hot air, two irons or hot tweezers. Do not twist them off: corroded pads on this board lift easily.<ref name="adam" /><ref name="sd12316" />
# Clean off the electrolyte and corrosion, neutralise, rinse with isopropyl alcohol and dry. Look under nearby parts as well: Philip Pemberton found leakage under the crystal X6 that stopped the BMU, and had to remove X6 to clean beneath it.<ref name="theofaults" />
# Check the tracks and vias around each position with a meter and repair any break.
# Fit new parts of the same capacitance and the same or higher voltage, with the polarity matching the board marking. Where pads have gone, Adam Wilson fitted the part to the vias on the other side of the board and secured it with epoxy.<ref name="adam" />
# After reassembly, check that the battery gauge works with the adaptor connected and that the machine starts.

Adam Wilson replaced the electrolytics with solid tantalum parts, which do not leak.<ref name="adam" /> Aluminium replacements of the original values are also used. Whichever you choose, keep at least Acorn's voltage rating.

See [[Capacitor Failure Symptoms]] and [[Battery Explosion, Capacitor or Corrosion Damage]].