Circuit diagrams


The contents of this part of the ftp server hierarchy are entirely the concern of their owner, and are generated, modified and maintained entirely by him in his spare time. They do not contribute to any official or authorised Acorn project.

Neither the author nor Acorn makes any recommendation, implicit or otherwise, for users to carry out their own modifications or servicing of Acorn hardware. If you have a machine which is not working and you are not confident in your ability to fault-trace a motherboard and perform any modifications which emerge as being necessary as a result of correct diagnosis, you should take your machine to an authorised Acorn service centre.

However, if (like me) you are one of those people who carries a logic probe "just in case" and has a decent dual-beam CRO (with service manual) at home, please follow the safety procedures detailed in the /pub/documents/safety/* hierarchy on this server. Power supplies and monitors are safety-critical items, and are NOT TO BE SERVICED except by qualified personnel, hence details of their internals are omitted from this collection.

Acorn accepts no responsibility for the correctness or legibility of the information presented. The information is presented in good faith by the file owner, to whom all problems should be reported.

Dave Walker 8/06/95

The service I am contemplating providing is an online library of Acorn circuit diagrams. Obviously I can't provide circuit diagrams of our current hardware (these matters are in the realm of our service centres), so instead I would like to provide (eventually) circuit diagrams for:

  • All the System range (1, 2, 3 and 5)
  • Atom
  • BBC Models A and B (several issues)
  • BBC Model B (US variant)
  • BBC Model B+
  • Z80, 6502 and 32016 Second Processors
  • Model B / Master Hard disc interface
  • Master 128
  • Master Turbo
  • Master AIV (the Domesday system)
  • Econet interface
  • Archimedes 300 series
  • Archimedes 400 series
  • Archimedes 400/1 series
  • Archimedes 540

Please note that this list is provisional and subject to change; right now,

are available for download.

I'm doing this for two reasons:

1. this service is something I would want to see if I was an external user
2. nobody else (to my knowledge) has done it before.


Most of the circuit diagrams for these machines only exist in paper form (at least, they only did until I digitised them). If your feedback convinces me this service would be valuable, I can do some further experimentation to see if I can successfully outline these diagrams into Drawfiles. As it is, for simplicity and compactness, the sprites have been turned into GIF87s (to be viewed using xv, etc). Experimentation showed me that the images are sufficiently huge that !ChangeFSI cannot cope with the image tables required for GIF > Sprite translation on an 8Mb machine, so I have also supplied the original sprites, archived using SparkFS (and decompressable using !SparkPlug, which can be built by downloading and running /pub/riscos/releases/dearchive.bas from this system).

Each sheet of the diagrams tends to be A3 (landscape) size; as I have an A4 scanner, each sheet has ben scanned in two halves. Files named "Part1" are the left hand side, and files named "Part2" are the right hand side of a given sheet.


The intention is to expand this collection to something approaching a reasonable size, if users would find such a resource useful. If you have any comments, feedback, hints on image processing to improve the quality of the diagrams, (reasonable!) requests for specific diagrams, etcetera please email me (dwalker@acorn.co.uk) with details.

Happy hacking, Dave Walker

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