Acorn Archimedes A400 Series (A440) and A400/1 Series (A410/1, A420/1, A440/1)
This page is a quick jumping-off point for repair, troubleshooting, and technical documentation for Acorn’s “professional” Archimedes desktop systems commonly grouped as the A400 and A400/1 families.
Overview
The original A400 series is best-known for the Archimedes A440 (top-end model), which shipped with Arthur originally and includes a built-in ST506/MFM hard disk interface. It was soon superseded by the improved A400/1 range.
The A400/1 series (A410/1, A420/1, A440/1) is an updated refresh of the earlier A400 range and introduced the MEMC1a memory controller. These machines are frequently upgraded in the field, so do expect “mixed” configurations.
Models and typical factory specs
| Family | Model | RAM (typical) | Storage (factory) | Notes |
|---|---|---|---|---|
| A400 | A440 | 4MB | ~20MB ST506/MFM hard drive + 3.5" floppy | Shipped with Arthur 1.2 originally; built-in ST506/MFM controller; 4-slot backplane. |
| A400 | A410 | 1MB | Floppy | Was announced; may be rare in the wild (often reported as not commonly sold). |
| A400/1 | A410/1 | 1MB | Floppy | Entry-level A400/1; can be upgraded (official kits existed) to A440/1-like spec. |
| A400/1 | A420/1 | 2MB | 20MB ST506 hard drive + floppy | Mid-range A400/1; typically factory-fitted internal MFM drive. |
| A400/1 | A440/1 | 4MB | 50MB ST506 hard drive + floppy | Top A400/1; “maxed out” from factory compared to other /1 models. |
Tip: Check the front badge and the bottom label / product code; it’s common to find machines that have been upgraded or re-labeled during service life.
Hardware notes
- CPU: ARM2-based (commonly 8MHz on these generations). ARM3 upgrades are common on surviving machines.
- Memory controller: A440 examples are commonly MEMC1; A400/1 machines introduced MEMC1a.
- Graphics/sound: VIDC-based video + multi-voice sound; many machines have a VIDC “enhancer” fitted.
- Expansion: Internal backplane typically provides up to 4 podule slots, and many systems have podules fitted for SCSI/IDE, Ethernet, user-port, second floppy, etc.
- Hard disk interface (factory): A440 has built-in ST506/MFM support; A420/1 and A440/1 shipped with internal ST506 drives from factory (A410/1 commonly shipped without a hard disk).
Ports and connectors (typical)
Port layout varies slightly with options fitted, but a common A400/1 rear-panel set includes:
- SYNC + MONO (high-resolution monochrome monitor options)
- Analogue RGB (colour monitor)
- Serial
- Headphones
- Parallel printer
- Econet (often “not fitted” unless the module is installed)
Common issues and preventative maintenance
1) RTC/CMOS batteries (A300/A400/A400/1 families)
- These machines commonly use 2 × AA batteries for CMOS/RTC backup in an off-board holder inside the case. This placement reduces the chance of motherboard destruction versus later on-board battery designs.
- Still, battery leakage can corrode the holder/contacts and wiring. Plan on replacing batteries roughly yearly and inspect the holder for alkali residue.
- If the holder is damaged: replace it rather than “forcing” batteries to fit. (Retro Kit documents a practical replacement approach.)
2) Capacitors and PSU age-related faults
- Expect age-related capacitor issues across the Archimedes line (symptoms can include unstable boot, audio issues, video instability, or intermittent faults).
- If your unit has been stored for years: inspect for obvious leakage/bulging and consider a cautious power-up strategy.
3) ST506/MFM hard disks
- Factory MFM drives are now elderly; failures and stiction are common. If you want to preserve data, avoid repeated power-cycling and consider imaging/recovery sooner rather than later.
- Many owners modernise storage via SCSI/IDE podules with CF/SD solutions.
4) Podules/backplane and internal connectors
- Reseat podules and inspect the backplane connector seating if you have crashes, missing devices, or boot issues.
- Check ribbon cables (floppy + MFM) for pin damage, oxidation, and strain.
Basic diagnostics flow
- Safety first: unplug before opening. Be careful around CRT monitor setups and mains PSU areas.
- Minimal configuration: remove non-essential podules; boot with keyboard/mouse/video only.
- Battery area inspection: check the AA holder/contacts and the wiring for corrosion.
- Visual inspection: look for capacitor leakage, burnt components, damaged cables, and corrosion.
- Storage isolation: disconnect the MFM drive if you suspect it’s dragging the PSU down or hanging boot.
- Use the service manual: follow the “dead computer” checks, functional tests, and backplane tests.
Manuals and documents
- Acorn A400/1 & R140 Service Manual (Internet Archive item) (includes fault-finding, disassembly, tests, and circuit diagrams)
- Direct PDF: A400/1 & R140 Service Manual
- Acorn Archimedes A440 Service Manual (Internet Archive item)
- Direct PDF: A440 Service Manual
- Archimedes 400 Series Welcome Guide (PDF)
- Archimedes Welcome Guide (RISC OS 2) (PDF)
- APP223: The New Archimedes 400/1 Series (brochure PDF)
- APP136: Archimedes 440 brochure (PDF)