Editing Sinclair ZX81 Capacitor Replacement Guide (section)

=== Choosing replacements ===

* '''C3''' — 22 µF, 16 V or higher. It sits on the raw input, which is nominally 9 V DC and rises to about 14 V open-circuit, so 16 V is the floor, not a suggestion.<ref name="zx81man" /><ref name="kio81">''Sinclair ZX81 Connectors'', The Sinclair ZX Computers Archive, k1.spdns.de. Secondary source: the ZX81 power connector is a 3.5 mm mono jack, centre pin +9 V and shaft ground, with an open-circuit voltage of about 14 V.</ref>
* '''C5''' — 1 µF. Sinclair specified 5 V minimum; it sits on the 5 V rail, and any modern 16 V or 25 V part is fine.
* Use 105 °C aluminium electrolytics from a recognised manufacturer. Equal capacitance, equal or higher voltage.
* Sinclair's originals are axial. Radial parts fit if you form and sleeve the leads so nothing can short to a neighbouring track.
* No lead-pitch figures are given here because Sinclair did not publish any; measure your own board.