Editing Sinclair QL Capacitor Replacement Guide (section)

== Is the QL a recap candidate? ==

The QL is '''not''' a machine with a systematic capacitor-failure problem in the way the later surface-mount Acorn machines are. Its electrolytics are conventional leaded axial and radial parts, and the great majority of the board's capacitors are ceramic decouplers that do not fail.

A recap is nevertheless reasonable on a forty-year-old machine, and there are specific cases where capacitors are directly implicated:

* '''Supply smoothing''' — C37, C39 (both 470 µF) and C35 (100 µF) carry the rectified feeds; ageing here shows up as ripple, instability and random crashes.
* '''Regulator input/output''' — C41 (0.33 µF) and C42 (47 µF) around the 7805; C38 (4.7 µF) on the +12 V regulator. These are the Service Manual's supply test points, so out-of-spec readings there point straight at them.<ref name="sm" />
* '''TV picture drifting continuously''' — the Service Manual says to check '''C23, C24, C25''' (all 22 µF).<ref name="sm" />
* '''No colour TV output''' — check '''C35, C36''' along with R85/R86, and '''C29''' with R54 and the components around IC28.<ref name="sm" />
* '''Real-time clock failure''' — check '''C1''' (82 pF) and '''C53''' (22 pF, Issue 6 only) along with R91 and R80.<ref name="sm" />
* '''Microdrive read/write problems''' — check '''C15/C16''' and '''C17/C18''' on the Microdrive boards along with R35/R34 and R37/R36.<ref name="sm" />

Priority order on an unrestored machine: the supply electrolytics first, then anything visibly aged, then the specific parts named above if the matching symptom is present.