Editing Acorn System 3 Troubleshooting Guide

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[[File:Acorn System 3.jpg|thumb|360x360px|Acorn System 3, a disc-based Eurocard system.]]

This guide gives diagnosis for the '''[[Acorn System 3]]''' (1980). The System 3 is a Eurocard rack, so diagnose by card (as for the [[Acorn System 2 Troubleshooting Guide|System 2]]) and add the floppy-disc subsystem. The CPU and cassette cards are the [[Acorn System 1]] cards.<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 Intel 8271 floppy controller and the shared card detail.</ref>

== Method ==

Reduce to a minimum (CPU + memory/BASIC + VDU) and confirm the machine boots BASIC; then add the FDC card and drive. A fault that appears with one card isolates to it or its slot. Confirm the backplane rails at an empty slot first.

== No display / no boot ==

Use the [[Acorn System 2 Troubleshooting Guide]] for the CPU, memory and VDU cards: verify the 1&nbsp;MHz clock and 6502, the BASIC ROM and RAM, and the MC6845/SAA5050 on the VDU card.

== Floppy-disc faults ==

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{| class="wikitable styled-table" style="width:100%; text-align:left;"
! Symptom !! Probable cause !! Action
|-
| Disc not detected / no DOS prompt || FDC card, ribbon cable, or drive || Reseat the 8271 and the ribbon; check drive power; try a known-good drive
|-
| Reads own discs, not others || Head alignment || Align with a reference disc
|-
| Read/seek errors || Dirty head, worn belt, or media || Clean the head; check the belt; try known-good media
|-
| DOS will not load || DOS ROM or its select || Reseat the DOS ROM; verify the FDC card links
|}

The floppy controller is the Intel 8271; reseat it and verify the disc-side cable before condemning the card.<ref name="cat" />

== 6809 / FLEX systems ==

A System 3 fitted with the 6809 CPU card runs FLEX. If such a machine will not boot, confirm which CPU card is fitted and that the matching OS ROM/disc is present; the 6502 and 6809 cards are not interchangeable without the corresponding software.<ref name="cat" />

== Backplane and connectors ==

A machine that works only when a card is pressed has a dirty or loose edge connector; clean the fingers and the backplane socket. Check the backplane power-input joints.

== Common fault catalogue ==

* '''Dead, rails present''' &mdash; CPU card; apply the System 1 checks.
* '''Boots BASIC, no disc''' &mdash; FDC card (8271), ribbon, or drive.
* '''Read/seek errors''' &mdash; head cleaning/alignment or media.
* '''No display''' &mdash; VDU card or monitor.
* '''Intermittent when jostled''' &mdash; dirty edge connector or backplane joint.

== Related pages ==

* [[Acorn System 3]]
* [[Acorn System 3 Maintenance Guide]]
* [[Acorn System 3 Capacitor Replacement Guide]]
* [[Acorn System 2 Troubleshooting Guide]] · [[Acorn System 1 Troubleshooting Guide]]

== References ==

<references />

{{Navbox-AcornComputers|state=collapsed}}

[[Category:Acorn Computers]]
[[Category:Troubleshooting Guides]]