Editing Acorn System 2 Maintenance Guide

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[[File:Acorn System 2.jpg|thumb|360x360px|Acorn System 2 in a 19-inch card frame with an 8-slot backplane.]]

This guide covers preventive maintenance for the '''[[Acorn System 2]]''' (1980), a rack-mounted Eurocard machine. The System 2 is a collection of Eurocards on an 8-slot backplane, so maintenance is largely per-card: edge-connector integrity, the on-card +5&nbsp;V regulators, socket reseating, and the backplane and power supply.<ref name="cat">[[Acorn System Catalogue]] and [[Acorn System 1 Technical Manual]], Acorn Computers &mdash; hosted on this wiki. Source for the Eurocard set, the per-card LM340-type +5&nbsp;V regulators, and the CPU/cassette card detail shared with the [[Acorn System 1]].</ref>

== ⚠️ Safety ==

The Eurocards run on low-voltage rails from the backplane. If an Acorn mains power supply is fitted, '''that PSU contains mains voltage''' &mdash; disconnect the mains lead before working near it, and treat its primary side as live. The cards themselves carry no mains and no CRT.

== Cards ==

A typical System 2 has four Eurocards: the 1&nbsp;MHz 6502 CPU card (with 2&nbsp;KB Cassette Operating System), a 40×25 teletext VDU card (MC6845 + SAA5050), a cassette interface card, and a memory card (4&nbsp;KB RAM + 4&nbsp;KB Acorn System BASIC ROM).<ref name="cat" /> The CPU and cassette cards are the same as the [[Acorn System 1]]; their maintenance is covered in the [[Acorn System 1 Maintenance Guide]].

== Maintenance ==

* '''Backplane and edge connectors''': clean each card's EuroConnector fingers and the backplane sockets with a soft eraser or contact cleaner. Oxidised edge connectors are the most common cause of intermittent faults on a racked system. Reseat each card firmly.
* '''On-card regulators''': each card regulates its own +5&nbsp;V with an LM340-type regulator. Verify +5&nbsp;V on each card and confirm the regulator heatsinks are fitted.
* '''IC reseating''': the cards are socketed; reseat the 6502, ROMs, RAM and the VDU's MC6845/SAA5050.
* '''VDU card''': clean the video output connector; the 40×25 teletext display uses the SAA5050 character generator.
* '''Cassette and keyboard''': keep the cassette DIN socket and the external keyboard connector clean.

== Capacitor health ==

Each Eurocard carries ceramic decouplers plus a regulator electrolytic; the CPU and cassette cards use the System 1 values (a 15&nbsp;µF/16&nbsp;V electrolytic each). See [[Acorn System 2 Capacitor Replacement Guide]].

== Recommended tools ==

* Screwdrivers and an anti-static strap; DC multimeter for the +5&nbsp;V checks.
* Contact cleaner and a soft eraser for the EuroConnectors and backplane.
* Temperature-controlled soldering iron and solder wick for the per-card electrolytics.

See [[Recommended Tools]] for the general toolkit.

== Preventive maintenance checklist ==

# Clean the backplane sockets and each card's edge fingers; reseat all cards.
# Verify +5&nbsp;V on each card; confirm regulator heatsinks.
# Reseat socketed ICs (6502, ROMs, RAM, MC6845/SAA5050).
# Clean the cassette DIN and keyboard connectors.
# If an Acorn mains PSU is fitted, inspect it (mains) and consider its electrolytics.

== Related pages ==

* [[Acorn System 2]]
* [[Acorn System 2 Troubleshooting Guide]]
* [[Acorn System 2 Capacitor Replacement Guide]]
* [[Acorn System 1 Maintenance Guide]] &mdash; the shared CPU/cassette cards
* [[Acorn System Catalogue]] · [[Capacitor Failure Symptoms]] · [[Recommended Tools]]

== References ==

<references />

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[[Category:Acorn Computers]]
[[Category:Maintenance Guides]]