Sinclair ZX81 Service and Assembly Manual
The Sinclair ZX81 Service and Assembly Manual is the manual Sinclair Research supplied with the Sinclair ZX81 kit. It is short — 43 pages — but it is the authoritative published record of what is actually fitted to a ZX81 board, because it contains Sinclair's own component lists giving the value, marking and type of every resistor, capacitor and semiconductor by designator.
It is the primary reference for Sinclair ZX81 Capacitor Replacement Guide and Sinclair ZX81 General Maintenance.
Two things in it are regularly got wrong elsewhere and are worth quoting directly:
- The ZX81 has only two electrolytic capacitors — C3 (22 µF, 16 V minimum) and C5 (1 µF, 5 V minimum). Everything else on the board is a ceramic disc.
- The power supply specification is "D.C. only — positive to the tip of the 3.5 mm jack plug. Need not be regulated, but should be well smoothed. Voltage — between 12 volts maximum and about 8 volts minimum (depending on smoothing) when on load. Current — not less than 600 mA, or 1.2 A if the printer is to work from the same supply."
Contents
edit| Section | Covers |
|---|---|
| 1–5 | Kit assembly: component identification, board population order, soldering the regulator and heatsink, testing before casing |
| 6 | Fault finding — the checks Sinclair told kit builders to make, including regulator temperature, tuning and the keyboard tails |
| 7 | Case assembly, including which screw goes in which hole |
| 8 | Component lists — resistors, resistor packs, capacitors, semiconductors and miscellaneous parts, by designator |
| 9 | Power supply specification |
| 10 | Sinclair's own repair service terms |
The manual also contains the ZX81 circuit diagram and PCB layout. A full-resolution copy of the circuit diagram is hosted separately at File:Sinclair ZX81 circuit diagram.png.
Download the Sinclair ZX81 Service and Assembly Manual here: Sinclair ZX81 Service and Assembly Manual.pdf