Sinclair ZX80 Assembly Instructions
The ZX80 assembly instructions are Sinclair's nine-page leaflet supplied with the Sinclair ZX80 kit, printed "© Sinclair Research Ltd 1980". The service address is the ZX80 Service Department, Science of Cambridge Ltd., 6 King's Parade, Cambridge.
Contents
[edit | edit source]- 1 Preparation
- 2 Precautions
- 3 Assembly
- 4 Suggested construction order
- 5 Testing
- 6 Power supply: 7 to 12 V DC, tip positive, 350 to 500 mA
- 7 Faults
- 8 Options: the white-on-black display link
- 9 Component list: every resistor, capacitor and semiconductor by designator, with alternatives
- 10 Miscellaneous parts
- 11 Service
- Last page: the component location drawing of the Issue 2 board
What this document does not contain
[edit | edit source]No circuit diagram. Sinclair's ZX80 circuit diagram is hosted as File:Sinclair ZX80 circuit diagram.png. The equivalent ZX81 booklet is Sinclair ZX81 Assembly Instructions. A different edition of the leaflet in the Ferranti Archives 2026 does include a circuit diagram; see below.
The Ferranti Archives 2026 copy
[edit | edit source]The Ferranti Archives 2026 holds another copy of the leaflet, found in Ferranti's "ZX81 Memory" folder: ZX80-SIN-LIT-130.[1] It is a colour scan, at much higher resolution, of the whole sheet printed on both sides: sections 1 to 11, the component location drawing of the Issue 2 board, and on the back of that drawing the ZX80 circuit diagram. Fold shadows cross every page and the reverse shows through, but the text is readable.
It is a different edition from the copy hosted above. Both carry "© Sinclair Research Ltd. 1980", but the text differs in these places:[1][2]
| Item | Ferranti Archives copy (ZX80-SIN-LIT-130) | Copy hosted above |
|---|---|---|
| Section 2, precautions | Four precautions | Adds a fifth: the white component-location markings for C3, C9, C11, C14 and C15 differ slightly from those of the other capacitors, referring to diagrams A and B on the reverse of the sheet |
| Fig. 1, IC orientation | Pin 1 marking only | Adds an alternative marking and a note that some ICs may only have a mark above pin 1 |
| Section 4, step 2 | "The resistors, diodes and capacitors" | Adds that D1 and D2 are not used |
| Section 6, supply voltage | 7 to 11 V | 7 to 12 V |
| Section 7, last fault check | If the picture jitters and the TV controls do not cure it, experiment with the value of C15 | If there is still no cursor, remove all ICs and check with an ohmmeter for a solder bridge between the IC socket pins and the tracks running between them |
| C15 | 220p, "may be from 0 - 330p (see text)" | "33p for USA (60 Hz)" |
| IC2 (ROM) | 2332 | 8332 or TMS 4732, "may be alternatively labelled" |
| IC10 | 74LS36x, the last digit overwritten by a pen tick | 74LS367 or 74LS365 |
| Diodes | D1 to D10 BA220 or BA221 (D1 and D2 not used) | D3 to D10 BA220, BA221 or IN4448, with an extra colour marking listed |
| Section 11, service | No refund clause | The service fee is returned if the fault was caused by faulty components supplied |
Every change in the hosted copy adds an option or a check, or corrects an entry, so the archive copy is probably the earlier printing; neither is dated more closely than 1980.
The circuit diagram
[edit | edit source]The circuit diagram on the back of the archive copy, headed "ZX80 circuit diagram", shows the edge connector pin-out, the power input marked "9V-11V" with C8 (22 µF 16 V) and the IC22 regulator, the modulator with R30 (1K) on video and R32 (330 ohm) on sync, the EAR and MIC networks, the 780-1 CPU (IC1) with 1K resistors R4 to R12 in the data lines, the ROM (IC2), the two 2114 RAMs (IC3, IC4), the keyboard buffer IC10 with the matrix diodes D3 to D10, D11 marked "USA 60Hz 525 lines only", the 6.5 MHz ceramic resonator X1 with C15 (0 to 330 pF), and an IC type table.[1] Points to be aware of when tracing a fault from it:
- The IC table gives IC7 as 74LS167 and IC9 as 74LS166; the component list gives 74LS157 and 74LS165. The right-hand edge of the table is cut off in the scan, so the IC14, IC15 and IC18 entries are uncertain.
- The drawing does not show /WR connected to pin 10 (write enable) of the 2114 RAMs IC3 and IC4. The circuit diagram hosted separately as File:Sinclair ZX80 circuit diagram.png shows "WR 10" on both, so use that drawing when tracing a RAM write fault.
- It differs from that separately hosted drawing in other details: the modulator is labelled only "Modulator" (the other drawing has "UM 1233 Modulator"), C12 is 100n (47N on the other drawing) and IC2 is 2332 (8332).
Pages that cite this document
[edit | edit source]- Sinclair ZX80: cites Section 6, Section 7, Section 8, Section 9
- Sinclair ZX80 Capacitor Replacement Guide: cites Section 3, Section 4, Section 6, Section 9
- Sinclair ZX80 General Maintenance: cites Section 2, Section 4, Section 5, Section 6, Section 7
- Sinclair ZX80 Troubleshooting Guide: cites Section 5, Section 6, Section 7, Section 9
- Sinclair ZX81 Assembly Instructions
Download: Sinclair ZX80 Assembly Instructions.pdf
References
[edit | edit source]- ↑ 1.0 1.1 1.2 Sinclair ZX80 assembly instructions with circuit diagram, 1980, Ferranti Archives 2026 (ZX80-SIN-LIT-130). Source for the archive copy's text, component list and circuit diagram.
- ↑ File:Sinclair ZX80 Assembly Instructions.pdf. Source for the hosted copy's text in the right-hand column.