Jump to content

Archimedes 300 Series Service Manual

From RetroTechCollection

The Archimedes 300 Series Module Level Service Manual is Acorn Computers' dealer service manual for the A305 and A310: part number 0476,140, issue 1, April 1988, produced by DAW Publications. It is written for fault-finding to module level, the modules being the main PCB, the PSU, the floppy drives, podules, the backplane, the keyboard, the mouse and the monitor.[1][2] The hosted PDF is 127 pages; between sections 4 and 5 it includes the separately printed upgrade leaflets, which carry their own page numbers.

Contents

[edit | edit source]

Page numbers are from the manual's contents list.[3]

  • 1. Introduction, p. 5: nature and purpose of the manual; technical specification; packaging and installation (p. 10)
  • 2. System description, p. 11
  • 3. Disassembly and assembly, p. 14: main unit and keyboard
  • 4. Upgrading, p. 18: leaflets for the backplane and fan, Econet module, podules, 0.5 MB RAM upgrade, second floppy drive, hard disc, MIDI module and Arthur ROM fitting
  • 5. Connectors, interfaces, links and test points, p. 19
  • 6. Fault-finding information, p. 25
  • 7. Appendices, p. 30: modules and dealer-serviceable parts (p. 31), production and field changes (p. 32), serial port application note (p. 35), test instructions (p. 37), sample service report (p. 73), function map (p. 74), plugs and sockets (p. 75), links and test points (p. 76), main PCB component layout (p. 77), final assembly and lower case assembly drawings (pp. 78-79), and the two-sheet main PCB circuit diagram (p. 80)

Specification

[edit | edit source]
Archimedes 305 and 310 as specified by Acorn[4]
Item Value
Chip set ARM (2 µm) processor, MEMC memory controller, VIDC video and sound controller, IOC input/output controller
Clock 24 MHz master oscillator; ARM at 4/8 MHz, typically 4 MIPS
RAM 305: 512 KB; 310: 1 MB; sixteen 64K × 4 DRAMs (120 ns) fitted, sixteen more as the 305 upgrade
ROM Four 32-pin sockets; 512 KB fitted as standard
Clock and CMOS RAM Real-time clock and 240 bytes of non-volatile RAM, kept alive by two LR06 (AA) 1.5 V manganese alkaline cells inside the main unit, which Acorn says require replacement once a year
Mains input 198-264 V AC (220/240 V nominal), 47-63 Hz; 0.4 A without monitor, 0.9 A with
Monitor outlet Unswitched IEC outlet, 3 A continuous, 80 A surge
Plug fuse 5 A to BS1362

What it settles

[edit | edit source]

The PSU feeds the main PCB through four 6.3 mm tabs: PL5 +12 V, PL6 0 V, PL7 +5 V and PL8 −5 V. The battery connects at PL11 and the fan at PL12.[5] Section 5 also gives the pinouts and signal levels of every external connector, including RGB at 0-0.7 V into 75 Ω.[6]

The PSU is a replaceable module, part 0176,002. A PSU that clicks indicates either a short between two of its outputs or a faulty PSU. After refitting or replacing an assembly, Acorn requires an earth continuity check at 25 A from the mains plug's earth pin to the base, rear panels and top cover.[2][7] Replacement PSUs made by Sanken have a screw head that can foul the rear-panel busbar, which may need filing to clear it.[8]

The production and field change notes are component-level fixes:[8]

  • No audio from the output socket: inserting a jack momentarily shorts output transistors Q9 and Q11 to 0 V. Boards with BC239s there should be changed; later boards use 2N3904s, which tolerate it.
  • Mono video fault on some issue 2 boards: check for insulating tape under the RGB connector bracket, then for a short from the mono video track to earth.
  • Speaker hum (FCO E008): a 100 µF capacitor of 10 V or more between pins 7 (+) and 4 (−) of IC68. Machines 27-AKB10-1000001 to -1001277 and 27-AKB15-1000001 to -1001752 left the factory without it.
  • RGB levels too low for some multisync monitors (FCO E009): R20, R41 and R59 become 43.2 Ω 1 %, and R39 is removed. Sync on green is no longer provided.
  • Video noise (FCO E011): a 1N4148 across R67, cathode towards Q13, and the decoupling capacitor 'A' nearest IC17 replaced by a 22 µF 6.3 V axial electrolytic.

Acorn warns that components on the four-layer main board should be removed only with vacuum desoldering equipment, or by cutting the leads and soldering the new part to the stubs.[8]

With a full white screen, VIDC IC17 pins 39, 40 and 41 should all carry the same signal. A battery-backed RAM failure in the functional test means checking the batteries, holder and connections before the board.[2]

What it does not contain

[edit | edit source]

It works to module level and gives no per-designator resistor or capacitor values; those are in the Archimedes 300 Series Service Manual Component Level Supplement. The PSU appears only as a module and there is no PSU circuit diagram. The software it describes is the Arthur operating system.[4] The PDF's text was produced by OCR (OmniPage), so check figures against the page images where they matter.

Pages that cite this document

[edit | edit source]

Download: Archimedes 300 Series Service Manual.pdf (8.6 MB)

References

[edit | edit source]
  1. ↑ Acorn Computers, High Performance Computer Systems 300 Series Module Level Service Manual, part 0476,140, issue 1, April 1988, cover and copyright page (PDF pp. 1-2). Hosted as File:Archimedes 300 Series Service Manual.pdf.
  2. ↑ 2.0 2.1 2.2 300 Series Module Level Service Manual, section 6, Fault-finding information, pp. 25-29 (PDF pp. 69-73).
  3. ↑ 300 Series Module Level Service Manual, Contents (PDF p. 3).
  4. ↑ 4.0 4.1 300 Series Module Level Service Manual, section 1.2, Technical Specification, pp. 5-8 (PDF pp. 5-8).
  5. ↑ 300 Series Module Level Service Manual, section 5.2, Plugs and sockets, p. 20 (PDF p. 64).
  6. ↑ 300 Series Module Level Service Manual, section 5, pp. 19-24 (PDF pp. 63-68).
  7. ↑ 300 Series Module Level Service Manual, section 7.1, Modules/Dealer Serviceable Parts, p. 31 (PDF p. 75).
  8. ↑ 8.0 8.1 8.2 300 Series Module Level Service Manual, section 7.2, Production and Field Changes, pp. 32-34 (PDF pp. 76-78).
Retrieved from "https://retrotechwiki.com/index.php?title=Archimedes_300_Series_Service_Manual&oldid=17637"