Editing Acorn A4 Capacitor Guide (section)

== Main board ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''A4 main board polarised capacitors (parts lists pp. 2-1, 2-2, 2-6, 2-7)'''
! Value !! Voltage !! Type !! Acorn part !! Designators !! Qty
|-
| 47 µF || 16 V || Aluminium, surface-mount || 0647,002 || C13, C38, C55, C57, C62, C66, C78, C89, C138 || 9
|-
| 10 µF || 16 V || Aluminium, surface-mount || 0647,001 || C19, C65, C67, C93, C108, C133, C135, C137 || 8
|-
| 4.7 µF || 25 V || Aluminium, surface-mount || 0647,000 || C107, C134, C136 || 3
|-
| 100 µF || 6.3 V || Aluminium, surface-mount || 0647,003 || C61, C97 || 2
|-
| 220 µF || 4 V || Aluminium, surface-mount || 0647,004 || C102 || 1
|-
| 1 µF || 16 V || Tantalum, surface-mount, 10 % || 0681,102 || C125 || 1
|}

Every other main board capacitor is a multilayer ceramic: 33 nF, 47 nF and 100 nF decouplers and small values from 15 pF to 22 nF. C75 is listed as a 150 nF ceramic in a 1210 case, although its part number (0681,050) is in the series Acorn uses for tantalums elsewhere in the list.<ref name="trm" /> On the circuit diagram C135 is on the BMU supply, and Philip Pemberton uses it as a test point for the BMU's 5 V.<ref name="drg">Acorn Computers, "Perth Main PCB" circuit diagram 0190,000/C, sheet 2 of 2: battery management (IC33, X6 4.1943 MHz, C135 10 µF on the BMU supply from Q2 LP2950), PL5 to PL7. Hosted on this wiki: [[:File:Acorn A4 Technical Reference Manual drawings.pdf]], page 2.</ref><ref name="theofaults" />

=== Other lists ===

Adam Wilson's published recap list for the A4 has 18 parts (eight 10 µF, seven 47 µF, two 100 µF and one 220 µF) and leaves out the three 4.7 µF 25 V positions and two of the 47 µF ones, yet his write-up describes losing the pads of C134, which Acorn lists as a 4.7 µF part.<ref name="adam">Wilson, Adam. [https://retrorepairsandrefurbs.com/2024/09/21/1992-acorn-a4-laptop-repair-restoration-modifications/ "1992 Acorn A4 Laptop Repair, Restoration, & Modifications"], Adam's Vintage Computer Restorations, September 2024 (retrieved 2026-10-01). "Eighteen SMD electrolytic capacitors"; replacement with solid tantalum parts; C134 and both its pads came off, so the replacement was fitted to the vias on the underside and secured with epoxy.</ref> Use Acorn's list above.