Editing Psion Organiser Capacitor Replacement Guide (section)

== What each capacitor does ==

Psion documented the [[Psion Organiser II|Organiser II]] power supply board in detail, and that board uses '''the same designator scheme and the same LM324-plus-reference-diode topology''' as the Series 1 board.<ref name="tech3">''Psion Organiser II Technical Manual'', Psion Ltd, 1986, Chapter 3 "Power Supply Board", transcribed at [https://www.jaapsch.net/psion/tech03.htm Jaap's Psion Organiser II Page]. Source for the functional descriptions of C1, C3, C6 and C8, the rail voltages, the 2–3 minute hold-up figure and the 21 V programming voltage behaviour. Applied here by analogy; Psion published no Series 1 circuit.</ref> The functional blocks below are therefore a strong guide to what the Series 1 parts are for — but '''verify against your own board before replacing anything'''.

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Functional blocks on the Organiser II power board, applied by analogy to the Series 1'''<ref name="tech3" />
! Designator (Organiser II) !! Function !! Failure symptom on a Series 1
|-
| '''C3''' || Decouples the always-on logic rail and, with the machine off, '''holds that rail above 3 V for two to three minutes''' after the battery is removed || The clock resets to 1 January on every battery change; RAM contents lost during a battery swap
|-
| '''C8''' || Series capacitor in the display-contrast charge pump, driven from a 1024 Hz square wave through the thumbwheel || No contrast control at all; blank or washed-out display that does not respond to the wheel
|-
| '''C1''' || Storage capacitor for the negative display rail (V_LCD), nominally adjustable between about +1.2 V and −3 V || Weak or drifting contrast; display fades as the machine warms up
|-
| '''C6''' || Storage capacitor in the Datapak programming voltage pump. Charged towards 35 V through an inductor, then regulated to '''21 V''' and applied in pulses. Must hold 21 V for 50 ms at 50 mA || '''Datapaks read normally but SAVE always fails.''' The classic signature
|}

Note that the Organiser II's electrolytics are the '''higher-numbered''' designators on its power board (C5, C6, C7, C8, C9, C10, C11, C15 in Psion's own parts list), while C1, C2, C3, C12, C13 are chip ceramics. The Series 1 board is leaded throughout, so the mapping is not one-to-one. Read your own board.