Editing Sinclair QL Capacitor Replacement Guide (section)

== Main board capacitors ==

Values are from Table 5.5 of the Service Manual. Where the Issue 6 board differs from Issue 5 it is noted; all other values are common to both.<ref name="sm" />

=== Electrolytics — the recap targets ===

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Sinclair QL main board — electrolytic capacitors'''
! Ref !! Value !! Rating !! Mounting !! Notes
|-
| C4 || 4.7 µF || 25 V, −10% +50% || Axial ||
|-
| C21 || 22 µF || 16 V || Radial ||
|-
| C22 || 22 µF || 16 V || Radial ||
|-
| C23 || 22 µF || 16 V, −10% +50% || Axial || Check if the TV picture drifts continuously
|-
| C24 || 22 µF || 16 V, −10% +50% || Axial || As C23
|-
| C25 || 22 µF || 16 V, −10% +50% || Axial || As C23
|-
| C35 || 100 µF || −10% +80% || Axial || Check if there is no colour TV output
|-
| C37 || 470 µF || 25 V, −10% +50% || Axial || Supply smoothing
|-
| C38 || 4.7 µF || 16 V || Radial || +12 V regulator output — a Service Manual test point
|-
| C39 || 470 µF || 25 V || Radial || Supply smoothing
|-
| C40 || 4.7 µF || 16 V || Radial ||
|-
| C41 || 0.33 µF || 50 V || Radial || +5 V regulator input — a Service Manual test point
|-
| C42 || 47 µF || 10 V || Radial || +5 V regulator output — a Service Manual test point
|-
| C47 || 22 µF || 16 V || Radial ||
|}

=== Ceramic and film capacitors — normally left alone ===

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Sinclair QL main board — non-electrolytic capacitors'''
! Ref !! Value !! Tolerance / rating !! Type
|-
| C1 || 82 pF || 5% || Ceramic — real-time clock network
|-
| C2 || 22 pF || 5% || Ceramic/TB
|-
| C19, C20 || 47 nF || 50 V || —
|-
| C26 || 0.01 µF || 20% || Ceramic/TB
|-
| C27, C28 || 0.1 µF || 50 V, −20% +80% || —
|-
| C29, C30 || 220 pF || 10% || — (C29: check if there is no colour TV output)
|-
| C31 || 16 pF (Issue 5) / '''22 pF (Issue 6)''' || 5% || Ceramic — adjusting this slightly can restore TV colour
|-
| C32 || 0.01 µF || 20% || Ceramic/TB
|-
| C33 || 0.1 µF || 50 V, −20% +80% || —
|-
| C34 || 47 pF || 5% || Ceramic/TB
|-
| C36 || 47 nF || 50 V || — (check if there is no colour TV output)
|-
| C43, C44, C46 || 0.1 µF || 50 V, −20% +80% || —
|-
| C45 || 1 nF || 2% || Ceramic
|-
| C48 || 0.01 µF || 20% || Ceramic/TB
|-
| C53 || '''Issue 6 only''' — 22 pF || 5% || Ceramic — replaced trimmer TC1; real-time clock
|-
| DC1–DC29 || 0.1 µF || 50 V, −20% +80% || Supply decoupling across the board
|}

'''Note on C53 and TC1.''' Pre-Issue 6 boards have a '''trimming capacitor TC1''' which allows the real-time clock oscillator frequency to be adjusted. At Issue 6 this was replaced by the fixed 22 pF capacitor C53.<ref name="sm" />