Editing Sinclair ZX Spectrum Capacitor Replacement Guide (section)

== Is the Spectrum a recap candidate? ==

'''No — not as a matter of course.''' The Spectrum uses ordinary leaded electrolytics and has no systematic capacitor-failure problem. There is no reason to shotgun every capacitor on a board that works.

Capacitors do nevertheless cause real, documented faults here, and Sinclair published a neat test for it: if the picture shows '''wavy lines''', press down on each electrolytic in turn with the machine running. If the lines disappear while you are pressing one, that is the faulty capacitor.<ref name="sm6">''ZX Spectrum Service Manual'', Sinclair Research Ltd, section 6 (fault diagnosis and repair - input/output), covering 6.1 TR4 faults, 6.2 no video, 6.3 corrupt paper, 6.4 video incorrect, 6.7 keyboard, 6.8 regulator coil and 6.9 speaker.</ref>

Worth attention on any board:

* '''C50''' and '''C34''' — the regulator input and output. These are Sinclair's own supply test points, so a rail that is out of tolerance or visibly rippling points straight at them.<ref name="sm5">''ZX Spectrum Service Manual'', Sinclair Research Ltd, section 5 (fault diagnosis and repair - PSU and memory): 5.2 power supply unit, 5.3.1 basic checks table, 5.4 memory check and the RAM bit-to-IC table, 5.5 keyboard structure.</ref>
* '''C44''' and '''C45''' — the rectifier smoothing for the +12 V and +12 VA rails produced by the TR4/TR5 inverter. C44 is one of the parts to check when the inverter has failed short.<ref name="sm6" /><ref name="iss3cd">''ZX Spectrum - Issue 3'' circuit diagram, Sinclair Research Ltd. Hosted on this wiki as [[:File:Sinclair ZX Spectrum Issue 3 circuit diagram.png]]. Source for circuit positions, rail derivation and the edge-connector pinout quoted on this page.</ref>
* '''C46''' — Sinclair specified this be replaced with a '''high-temperature''' component as a service modification, on all units.<ref name="sm4">''ZX Spectrum Service Manual'', Sinclair Research Ltd, section 4 (fault diagnosis and repair - getting started): 4.1.2 modification history, 4.2 modifications to the Issue 1 board, 4.3 modifications to the Issue 2 board, 4.4 modifications to the Issue 3B board, 4.5 the 32K extension memory, 4.6 Hitachi vs NEC ROM links; and section 8.2, notes to the parts list.</ref>
* '''C65''' — implicated by Sinclair in a dim picture, where it has gone high-impedance.<ref name="sm6" />
* Anything bulging, leaking, or that changes the symptom when you press it.