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Acorn Archimedes

The first consumer micro with an ARM CPU (1987) — yes, the ancestor of the ARM in our phones. RISC OS, 8-channel sound, and a few notable games (Elite, Zarch/Virus, Lander). Standard late-80s repair: recap, a leaking RTC battery, PSU RIFA.

Acorn A3000 (Archimedes)

Acorn A3000 (Archimedes) — photo by mikkohoo, CC BY-SA 4.0 (Wikimedia Commons).

Identification / models

Model Year CPU Note
A305 / A310 / A4x0 1987 ARM2 @ 8 MHz the original series
A3000 1989 ARM2 all-in-one keyboard (consumer)
A5000 1991 ARM3 @ 25 MHz faster, RISC OS 3
RiscPC 1994 ARM610/710… modular, the top of the range

Repair (technician)

  • Recap: PSU and board electrolytics (A3000/A5000 leak) → Recap.
  • RTC battery: an often-soldered battery that leaks and eats the board → remove/replace → backup batteries.
  • RIFA (mains filter): smokes/explodes → replace.
  • Floppy drive (3.5″): mechanism → clean / Gotek.
  • Video output: RGB (analog/TTL per model) → a suitable monitor / mods.

Procedure — a dead computer, step by step ✅

What this adds

Ordered for a home computer: what kills these is its power supply, its battery, its capacitors, its socketed RAM and its keyboard — roughly in that order, and well before the CPU. → PCB diagnosis

1. The power supply — measured before it is plugged in. This is the one step not to swap around. On a machine of this age a supply does not simply stop: a 5 V regulator that fails high puts 7, 9, 12 V onto the bus and takes the RAM and the custom chips with it. Measure every rail off the machine, under a dummy load if you can, and only then plug it in. This page documents RIFA capacitors on this machine: the mains filter caps that crack, then let go in smoke on the first power-up. Replace them before you switch on, not after.

2. The battery — before anything else. This page documents a cell that leaks — check on the page whether your model is one of the affected ones, several of these pages cover a whole range. Its electrolyte eats the copper underneath and keeps eating while the machine sits in a cupboard, so it comes out first, before any diagnosis. Neutralise, clean, then check continuity on the tracks around it — a machine that no longer boots after storage is very often this and nothing else. → Backup batteries

3. Capacitors. Recap is the default on these machines, not a last resort — and on the supply first, since that is what protects everything else. → Recap

4. RAM, on its sockets. These machines were built to be repaired: the RAM, and often the logic, sit in sockets. Reseat everything first — thirty years of oxide is a classic no-boot. Then swap chips: a bad RAM chip usually gives a repeatable pattern of garbage or a screen frozen at a fixed character.

5. The keyboard. A console does not have one; a computer's is a wear part. A membrane keyboard fails as whole dead rows or columns — that is the membrane, not the machine. A mechanical one wants its contacts cleaning, not replacing. Check this page: the failure mode is often documented per model.

6. Storage — tape or disk. Both often come down to the same things: a dirty head, and for tape the azimuth and a belt turned to tar. ⚠️ On the floppy side, check whether the mechanism actually has a belt before looking for one: many do, but some drives are direct drive, and hunting a belt that isn't there means stripping a drive for nothing. A machine that boots but loads nothing is a drive fault, not a logic fault — do not go looking on the board for it.

7. Video output. RF, composite, RGB or a dedicated monitor, depending on the machine (see Identification). Test with something else before you conclude: a period modulator and a modern TV disagree far more often than either is broken.

8. Still nothing. Now the logic: rails on the board, reset, clock, bus. → PCB diagnosis

Common faults

Symptom Likely cause Lead
Instability / crashes PSU/board caps Recap
Smoke at power-on PSU RIFA Replace the RIFA
Corrosion / wrong clock RTC battery Remove, repair traces
Floppy not read 3.5″ mechanism Clean / Gotek

Modernisation & mods — what to buy, how

Leaking RTC battery + RIFA

Remove the RTC battery immediately (it leaks and eats the board) → clock on an external lithium cell, clean/repair traces. Recap + replace the PSU RIFA caps (smoke).

Modern storage - Gotek + FlashFloppy or HxC 🟡 (3.5″ floppy emulation). - Hard disk → CF/SD 🟢: on IDE-controller models (A5000, RiscPC) a CF card on IDE replaces the mechanical disk; modern SCSI/IDE podules otherwise. RISC OS boots from the CF.

Video - Analog RGB/VGA output per model 🟢 → RGB2HDMI (Raspberry Pi) or a simple passive/active VGA→HDMI for a crisp modern display.

Expansion - Accelerator boards (ARM3) 🟠, RAM upgrades 🟡, networking podules (Ethernet) 🟢 — the Acorn expansion ecosystem is still active.

⚠️ Do not host RISC OS/games — method only.

Archived manufacturer documentation ✅

Manufacturer documentation archived locally.

  • Archimedes A3010 — PDF
  • Archimedes A3020 — PDF
  • Archimedes A4 — PDF
  • Archimedes A4000 — PDF
  • Archimedes A5000 — PDF

Status

Manufacturer documents with no explicit licence, kept for preservation.

See also

Sources & attribution

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.