RetroTechCollection

Acorn System 5 Maintenance Guide

This guide covers preventive maintenance for the Acorn System 5 (late 1982), the last of Acorn's rack-mounted Eurocard machines. It is a single extra-height 19-inch frame with up to ten Eurocard slots, two 5.25-inch floppy drives and an integral mains power supply. Maintenance is the per-card Eurocard work plus the floppy mechanism and the mains PSU. The Acorn System 5 Handbook is the primary reference.[1]

Acorn System 5 card cage and 10-slot backplane.

Safety: integral mains PSU

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The System 5 contains a mains-powered power supply feeding the backplane. Disconnect the mains lead before opening, and treat the PSU primary side as live. The Eurocards carry low-voltage rails only, and there is no CRT.

Cards and frame

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As standard the System 5 has a 1 MHz 6502 (a 2 MHz 6502A board was an option), 32 KB of DRAM, a floppy-disc controller (Intel 8271) and an 80×25 (or 40×25 teletext) VDU card, with the remaining slots free for an additional 16 KB DRAM card, an Econet adapter or interface cards.[1][2] The System keyboard plugs into the CPU card.

Maintenance

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  • Backplane and edge connectors: clean the 10-slot backplane sockets and each card's fingers; reseat firmly.
  • Per-card +5 V: verify the rail on each card; confirm regulator heatsinks. The 32 KB DRAM cards draw more current than the static-RAM cards — check their regulators.
  • Floppy drives: two 5.25-inch drives (e.g. 80-track) — clean the heads, check belts and the ribbon to the FDC card (see Acorn System 3 Maintenance Guide).
  • Econet: clean the Econet connectors and check the network termination if used as a server.
  • Mains PSU and cooling: keep the frame ventilated; inspect the PSU for ageing.

Capacitor health

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Each Eurocard carries a regulator electrolytic plus ceramic decouplers; the DRAM cards and the integral mains PSU are the main electrolytic sites. See Acorn System 5 Capacitor Replacement Guide.

Preventive maintenance checklist

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  1. Clean the 10-slot backplane and each card's edge fingers; reseat all cards.
  2. Verify +5 V on each card, especially the 32 KB DRAM cards.
  3. Clean both floppy heads; check belts and the FDC ribbon.
  4. Check the Econet connectors (if a server).
  5. Inspect the mains PSU; consider its electrolytics (mains caution).

The power supply is one exchange item

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Acorn's own documentation treats the System 5 supply as a single Aztec AC9231 switch-mode module rated +5 V 6 A, −5 V 0.5 A, +12 V 2.5 A and −12 V 0.5 A, carried as one exchange part. No component values are published for it — the same pattern as the BBC Micro supply. If you work on it, read the values off the fitted parts.[3]

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References

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  1. ↑ 1.0 1.1 Acorn System 5 Handbook (1 March 1983), Acorn Computers — hosted on this wiki. Source for the System 5 frame, the standard card set (6502/6502A CPU, VDU, 32K DRAM, floppy controller, Econet) and per-board detail.
  2. ↑ Whytehead, Chris. "Acorn System 5", Chris's Acorns / The Centre for Computing History. Source for the 10-slot card cage, the example configuration (2 MHz 6502A, 80×25 VDU, 32K DRAM cards, Econet, Intel 8271 controller, two 80-track drives) and the System keyboard connection.
  3. ↑ Recorded in this wiki's own verification of the Acorn documentation set: the System 5 supply appears in Acorn's documentation as an Aztec AC9231 module with rated outputs of +5 V 6 A, −5 V 0.5 A, +12 V 2.5 A and −12 V 0.5 A, carried as a single exchange item with no published component-level values.


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