Acorn Electron Service Manual
The Electron Service Manual is Acorn Computers' dealer service manual for the Acorn Electron, part no. 0405001, issue 2, dated January 1987 (first published 1984). The hosted scan has 54 PDF pages with a text layer. Acorn wrote it for "service engineers and Acorn dealers who will be servicing the Electron microcomputer on behalf of Acorn Computers Limited", and the copyright page says it remains Acorn's property and must be returned when a dealer's appointment ends.
Contents
[edit | edit source]Acorn's contents list, with the printed page numbers:
| Section | Page |
|---|---|
| 1 Introduction | 1 |
| 2 Packaging and installation (adaptor 19 V AC, 50 Hz, 14 W) | 2 |
| 3 Specification: computer, MOS, BASIC, power supply, cassette interface, video outputs, audio output, environment | 3–5 |
| 4 Disassembly and assembly | 6 |
| 5 Circuit description: general (clocking, DRAM organisation) and PCB links (LK3, LK4) | 7 |
| 6 The uncommitted logic array (ULA): function of each pin | 8 |
| 7 Electron test equipment (PIT test, Electron Watchdog) | 9 |
| 8 Fault finding inside a dead Electron: power supply, oscillator, ULA, CPU, ROM, DRAMs, video, cassette interface, keyboard, sound | 10–14 |
| Appendix: diagnostic flowcharts | 15–23 |
| Final assembly; Electron block diagram; functional block diagram of the ULA | 25–29 |
| Main PCB circuit diagram, layout and silk-screen | 31–35 |
| Electron power supply board circuit diagram | 37 |
| Keyboard matrix | 39 |
| Parts lists: keyboard assembly, final assembly, main PCB | 41–44 |
Chapter 8 gives Acorn's test figures: at least 17 V RMS from the adaptor, +5 V at 4.75–5.25 V with no more than 50 mV noise into a 10 Ω load, a main board draw of 700–900 mA from +5 V and about 25 mA from −5 V, and the supply and signal pins of the ULA, processor, ROM, DRAMs and oscillator. The video section includes scope settings for the modulator input waveform and the colour oscillator figure of 17.7345 MHz ±200 Hz.
What this manual does not contain
[edit | edit source]- No parts list for the power supply board. The board's circuit diagram (p. 37) shows the designators but no component values.
- Nothing on the later boards with the ULA soldered in. Section 8.3 describes the socketed ULA under its metal clip, and the circuit diagram is drawing 105,000/C from 1983.
- Nothing on the Plus 1, Plus 3 or other expansions, or on monitors and televisions.
- Nothing on the inside of the mains adaptor, which is a sealed transformer with a built-in plug.
What it settles
[edit | edit source]- The internal power supply board is a switching regulator (circuit diagram p. 37), not a 7805 linear regulator.
- The adaptor is 19 V AC at 14 W (p. 2); the faston tabs on the supply board marked 18V AC feed only the expansion connector (p. 6).
- The case opens from four screws underneath, and the machine will not run with the keyboard unplugged (p. 6).
- The main PCB electrolytic and tantalum values and Acorn part numbers (pp. 43–44).
Pages that cite this document
[edit | edit source]- Acorn Electron: specification, ICs, power supply and board figures
- Acorn Electron Maintenance Guide: disassembly, ULA removal, supply figures, keyboard parts
- Acorn Electron Troubleshooting Guide: the chapter 8 procedures and pin checks
- Acorn Electron Capacitor Replacement Guide: main PCB capacitor list and the supply test
Download: Acorn Electron Service Manual.pdf