Related Manuals for Sinclair ZX Spectrum
Summary of Contents for Sinclair ZX Spectrum
- Page 1 SINCLAIR ZX Spectrum ZX Spectrum+ Service Manual Edited by Brendan Alford Spectrum For Everyone Website https://spectrumforeveryone.com/ Spectrum For Everyone Facebook Group https://www.facebook.com/groups/spectrum4everyone/...
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Page 2: Table Of Contents
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ ONTENTS 1 Introduction ............................... 7 1.1 Introduction ............................7 1.2 Architecture ............................8 1.3 Z80A CPU ............................. 8 1.3.1 Data Bus ............................8 1.3.2 Address Bus ..........................8 1.3.3 Control Bus ........................... 8 1.3.4 CPU Clock ............................. - Page 3 Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 4 Fault Diagnosis and Repair – Getting Started ..................20 4.1 Introduction ............................20 4.1.1 Test Equipment .......................... 20 4.1.2 Modification History ........................21 4.2 Modifications - Issue 1 Board......................22 4.3 Modifications - Issue 2 Board......................
- Page 4 6.6.2 Blue haze around `Sinclair` logo....................34 6.6.3 Screen too yellow ........................34 6.6.4 Intermittent colour ........................34 6.6.5 Red, Blue or Green `Sinclair` logo ....................34 6.6.6 Washed out colours ........................34 6.7 Keyboard Faults ..........................34 6.7.1 KB1 fault ............................. 34 6.7.2 KB2 fault .............................
- Page 5 Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 7 Fault Diagnosis and Repair – Colour, Repair and Upgrades..............36 7.1 IC14 (LM1889) Pin Signals ......................... 36 7.2 Repair ..............................37 7.3 16k to 48k Upgrade ........................... 37 7.3.1 Integrated Circuits/Link Settings ....................37 7.3.2 Issue 2 Board ..........................
- Page 6 Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 9.9 Issue 6A Board ..........................50 9.10 Fault Finding – Servicing Addenda ....................50 9.11 Warranty Seal ..........................50 9.12 Parts Lists ............................50 9.12.1 Notes ............................50 9.13 Capacitors - Unless otherwise stated all are axial types ..............51 9.14 Coil ..............................
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Page 7: Introduction
1.1 I NTRODUCTION A block diagram of the complete ZX Spectrum micro-computer is given below. It is valid for all build standards, fitted with either 16k or 48k bytes of dynamic RAM memory. Although functionally identical, detailed circuit changes have been introduced to improve reliability and to assist with manufacture. The printed circuit board layout has also been modified. -
Page 8: Architecture
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 1.2 A RCHITECTURE The architecture of the Spectrum shown above is typical of many microcomputer systems in that it comprises a single microprocessor board (in this instance a Z80A or u780 CPU), a read only memory (ROM), an expandable RAM memory and an input/output section handling the keyboard, tape and TV display functions. -
Page 9: Cpu Clock
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 1.3.4 CPU Clock Returning to the CPU clock mentioned earlier in this section, the ULA is able to inhibit this input bringing the CPU to a temporary halt. This mechanism gives the ULA absolute priority, allowing it to access the standard 16k RAM without interference from the CPU (see RAM description). -
Page 10: Read/Write Operations
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 1.5 R RITE PERATIONS The following description should be read in conjunction with the circuit diagrams. 1.5.1 Read Only Memory (IC5) The CPU addresses the ROM directly during memory read cycles using the address bus A13-A0. MREQ and RD enable the ROM and the ROM outputs respectively. -
Page 11: Expansion Ram (Ic15-Ic32)
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 1.5.3 32k Expansion RAM (IC15-IC32) The eight 32k ICs making up the 32k x 8 bit expansion RAM are in fact 64k ICs with either row or column drop-out, rendering one half of the memory non-functional. In order to accommodate the Texas Instruments RAM (Type TMS 4532) or the optional OKI RAM (Type MSM3732) a set of links are provided, visible on the circuit diagram above the address multiplexer IC25/IC26. - Page 12 Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/...
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Page 13: Input/Output
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 1.6 I NPUT UTPUT The input/output section of the Spectrum is centered round the ULA (IC1). The functions performed within the device include TV video compilation, keyboard scanning and tape input/output. It also derives and controls the CPU clock (CPU) using an external 14 MHz crystal X1, and drives the loudspeaker when a ‘BEEP’... -
Page 14: Keyboard Scanning
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 1.8 K EYBOARD CANNING Every 20ms (i.e. once per maskable interrupt), the CPU systematically scans the keyboard recording which keys (if any) have been pressed. The scanning method is described below with the aid of the diagram below. -
Page 15: Tape Interface
1.11 P OWER UPPLIES The on-board power supply unit requires a 9V unregulated supply from the external Sinclair ZX power pack and derives the following internal supply rails: • Regulated +5V for the IC logic circuits, the ULA and the UHF modulator. -
Page 16: Disassembly/Assembly
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ ISASSEMBLY ASSEMBLY Disassembly Assembly 2.1 D ISASSEMBLY Unplug all input/output leads and turn the computer upside-down to reveal five self-tapping screws. Remove the screws. Hold the two halves of the case together and return the computer to the keys uppermost position. -
Page 17: Setting Up And System Test
Adjustment instructions apply strictly to the Issue 2 Spectrum boards only but are generally relevant to the Issue 1 Spectrum as well. To carry out the setting up procedure it is first necessary to remove the ZX Spectrum from the case (Section 2, Assembly/Disassembly). For convenience, the keyboard may also be disconnected. -
Page 18: Colour Adjustment
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 3.1.3 Colour Adjustment Potentiometers VR1 and VR2 are used to effectively null the voltages between pins 4 and 2 (for VR1) and pins 2 and 3 (for VR2) on IC14 (LM1889). To allow for thermal drift, the potentiometers are set for non- zero voltages;... -
Page 19: System Test
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 3.2 S YSTEM The system test for the Spectrum may be undertaken using the ZXTP taped program loaded conventionally; this requires that the keyboard is connected. The test should be carried out with the Spectrum connected to its own power supply. -
Page 20: Fault Diagnosis And Repair - Getting Started
NTRODUCTION 4.1.1 Test Equipment Sections 4 to 7 are intended as a guide to fault diagnosis and repair of the ZX Spectrum. It is assumed that users have a reasonable knowledge of electronic servicing, theory and standard fault-finding techniques and have access to the test equipment and tools required to carry out the task. The table below contains a list of the minimum recommended test equipment and materials. -
Page 21: Modification History
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 4.1.2 Modification History Two major modifications have been implemented on the Spectrum boards: (a) A modified layout of board (i.e. Issue 1, Issue 2 and Issue 3): Issue 1. This layout allowed for the 16k RAM to be mounted direct on the board, with the 32k extension consisting of a subsidiary board mounting onto special DIL connectors. -
Page 22: Modifications - Issue 1 Board
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 4.2 M ODIFICATIONS SSUE OARD A number of modifications were introduced, and these should be checked for and, if necessary, introduced retrospectively: • 100pF capacitor between RAS and ground - necessary only when using ULA 5C102. -
Page 23: Modifications - Issue 2 Board
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 4.3 M ODIFICATIONS SSUE OARD A number of modifications have also been introduced for the Issue 2 board. These should be checked and, if necessary, introduced retrospectively. • These components should be changed if colour quality needs upgrading:... -
Page 24: Board Issue 3
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 4.5.3 Board Issue 3: This allows OKI ICs to be used in place of TI 4532. Again, all ICs must be of the same designation. Appropriate links (2) must be fitted in the grid located on the board between the edge connector and the `mic` jack socket. -
Page 25: Fault Diagnosis And Repair - Psu And Memory
With a densely populated board such as the ZX Spectrum, as careful physical examination of the board can sometimes indicate an obvious fault. Burnt-out discrete components or an overheated track show up immediately, as do the attentions of an enthusiastic amateur. -
Page 26: Initialization
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 5.3 I NITIALIZATION At switch-on the computer should automatically initialise and produce a clear screen with the statement © 1982 Sinclair Research Ltd - displayed in the lower left section of the screen. This indicates that most of the system is working. If the Spectrum does not initialise, carry out the following basic checks. -
Page 27: Memory Check
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 5.3.1.2 (b) IC22 Pin 4 – RAS Pin 3 – WRITE Pin 15 - CAS If no fault has been found and the computer still has not initialised, the fault could lie in the RAM. If the computer is a 48k machine the 32k of expansion RAM can be isolated. -
Page 28: Example
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 5.4.1 Example If a 48k Spectrum is giving a memory of 25.25k key in the following instruction: PRINT PEEK 23732+PEEK 23733*256 Assume the answer displayed is 43200, therefore the faulty location is 43201 (stops at last valid location). -
Page 29: Keyboard Structure
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 5.5 K EYBOARD TRUCTURE The keyboard is connected horizontally in eight blocks of five keys and vertically in five blocks of eight keys. The diagram below shows the configuration. It follows that is any block of five keys fail the fault is with KB2 circuitry or the 8-way membrane, and that if any block of eight keys fail the fault is with KB1 circuitry or the 5-way membrane. -
Page 30: Fault Diagnosis And Repair - Input/Output
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ – I AULT IAGNOSIS AND EPAIR NPUT UTPUT TV screen dead, smoke appears on switch-on / Not Initializing No Video Corrupt Paper, after ULA change Video Incorrect Colour Tuning Faults (Issue 1 and Issue 2 boards) -
Page 31: No Video
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 6.2 N O VIDEO 6.2.1 No video Change IC1 Check TR1 and TR2 6.2.2 No video after ULA changed Visually check IC1 and socket Check for shorting between C65 and R53 Carry out Power Supply Unit check 6.2.3 No +5V input... -
Page 32: Corrupt Paper, After Ula Change
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 6.3 C ORRUPT APER AFTER CHANGE 6.3.1 Initial Check Check IC1 socket Check PWR socket is not intermittent Check IC1 pin 14 for +5V with no discernable ripple 6.3.2 No 3MHz at IC2 pin 6... -
Page 33: Distorted Video
6.5.5.3 IC14 pin 17 output correct but still no colour (All board Issue numbers) With `Sinclair` logo on screen IC14 pin 2 and IC14 pin 4 should be as follows: If IC14 pins 2 and 4 are correct, change modulator. -
Page 34: Pin Screen
If untunable (Issue 1 and Issue 2 boards) change IC14 6.6.3 Screen too yellow Change IC14 6.6.4 Intermittent colour Change TC2 (Issue 1 and Issue 2 boards) Change IC14 6.6.5 Red, Blue or Green `Sinclair` logo Change IC1 6.6.6 Washed out colours Check TR2 6.7 K EYBOARD AULTS 6.7.1 KB1 fault... -
Page 35: Speaker
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 6.9 S PEAKER 6.9.1 No speaker output Check load input waveforms Check TR7 Check D9 Change speaker 6.10 S PEAKER NPUT AVEFORMS... -
Page 36: Fault Diagnosis And Repair - Colour, Repair And Upgrades
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ – C AULT IAGNOSIS AND EPAIR OLOUR EPAIR AND PGRADES IC14 (LM1889) Pin Signals Repair 16k to 48k Upgrade Integrated Circuits/Link Settings Issue 2 Board Issue 3 Board 7.1 IC14 (LM1889) P IGNALS Pin No. -
Page 37: Repair
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ Notes: Rails and signals taken on switch-on, computer displaying `Sinclair` logo. No keys pressed All DC levels positive with respect to 0V 7.2 R EPAIR Renewal of components should be carried out using recognised desoldering/heatsinking techniques to prevent damage to the component or to the printed circuit board. -
Page 38: Issue 3 Board
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ Notes: • All external RAM ICs must be of the same type (i.e. all -3 or -4 variants) • LINK 3 on the board (IC26, pin 10) should be fitted if IC15-IC22 are type 4532-3 •... -
Page 39: Issue 3 Links Vs Ic Manufacturer And Type
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 7.3.4 Issue 3 Links vs IC Manufacturer and Type... -
Page 40: Expansion Memory Ic Locations
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 7.3.5 Expansion Memory IC Locations Shaded areas denote expansion IC locations. -
Page 41: Parts List
NTRODUCTION Parts lists for the ZX Spectrum are provided in table form; one for the case assembly and another for the board assembly. The latter covers the Issue 2 and 3 Spectrums and is related to the board layout diagrams available here and here. -
Page 42: General Capacitor Change
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 4. The introduction of alternative components for R24 and R27 is essential. At the same time C67 replaces D14 and R73 is added. 5. Issue 2 boards fitted with the Type 5C112 ULA have either a transistor (TR6) or diode/resistor modification (see Issue 2 circuit diagram for details). -
Page 43: Capacitors - All Axial Types Unless Otherwise Stated
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 8.5 C APACITORS LL AXIAL TYPES UNLESS OTHERWISE STATED Circuit Reference Issue 2 Issue 2 Mod Notes Issue 3 Rating/Tol. Type C1-C8 47nf 47nf 25V, 10% Ceramic 22uf 22uf 10V, -10%+80%... -
Page 44: Coil
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 8.6 C Circuit Reference Issue 2 Issue 2 Mod Notes Issue 3 Rating/Tol Type Coil SPECTRUM - SPECTRUM 1703 8.7 C ONNECTORS Reference Description Manufacturer/Part Number 3.5mm jack socket 3.5mm jack socket 2.1mm co-axial socket... -
Page 45: Resistors - All 1/4W, 5% Unless Otherwise Stated
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 8.11 R 1/4W, 5% ESISTORS UNLESS OTHERWISE STATED Circuit Reference Issue 2 Issue 2 Mod Notes Issue 3 Rating/Tol Issue 3B R1-R8 470R 470R R9-R16 R17-R23 330R 330R 180R 180R R26/R27... -
Page 46: Transistors
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 8.12 T RANSISTORS Circuit Reference Issue 2 Issue 2 Mod Notes Issue 3 TR1/TR2 ZTX313 ZTX313 ZTX313 ZTX313 ZTX650/TIPP31 ZTX313 ZTX213 ZTX213 ZTX313 ZTX313 ZTX450 TR8/TR9 BC184/BC549B 8.13 M ISCELLANEOUS Reference... -
Page 47: Supplement No. 1
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ UPPLEMENT Introduction DC-DC Converter Modification Issue 3B Board Issue 4 Board Issue 4A Board Issue 4B Board Issue 5 Board Issue 6 Board Issue 6A Board Fault-Finding - Servicing Addenda Warranty Seal... -
Page 48: Introduction
9.1 I NTRODUCTION In line with Sinclair`s policy of continual product improvement a number of changes to the Spectrum Printed Circuit board have been implemented. Since the Service Manual was published the printed circuit board has been upgraded through Issues 4A, 4B, 5 and is currently at Issue 6A. This supplement details the modifications, board by board and also provides additional servicing information and spare parts lists. -
Page 49: Circuit Operation
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ Substitute components as follows: Remove Substitute C79 (positive to ground) Open circuit D19 (positive to ground) D18 (positive to C46) R60, 220R 9.2.1 Circuit Operation The modification is confined to adding/changing protection components in the rectification circuit to improve reliability. -
Page 50: Issue 6 Board - None Issued
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 9.8 I SSUE OARD ONE ISSUED 9.9 I 6A B SSUE OARD This board is similar to Issue 5 but can be fitted with either a Ferranti or a Saga main ULA. The circuit diagram is shown here and the board layout is shown here. -
Page 51: Capacitors - Unless Otherwise Stated All Are Axial Types
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 9.13 C APACITORS NLESS OTHERWISE STATED ALL ARE AXIAL TYPES Circuit Ref Issue 4A Issue 4B Issue 5 Issue 6A Rating +/- Tol % Type C1-C8 22nf 22nf 22nf 22nf 25V, 10%... -
Page 52: Coil
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 9.14 C Circuit Ref Issue 4A/4B/5/6A Manufacturer Coil L1-L2 Spectrum TFR, 2 windings on toroidal former N. Devon 9.15 C ONNECTORS Reference Description Manufacturer/Part Number 3.5mm jack socket Tuda 3.5mm jack socket Tuda 2.1mm co-axial socket... -
Page 53: Resistors - 0.25W, 5% Tolerance Unless Otherwise Stated
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 9.17 R - 0.25W, 5% ESISTORS TOLERANCE UNLESS OTHERWISE STATED Circuit Ref Issue 4A Issue 4B Issue 5 Issue 6A Rating Tol% R1-R8 470R 470R 470R 470R R9-R16 R17-R23 330R 330R... -
Page 54: Diodes
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 9.18 D IODES Circuit Reference Issue 4a Issue 4b Issue 5 Issue 6a Type D1-D9 1N4148 1N4148 1N4148 1N4148 Signal NOT USED NOT USED NOT USED NOT USED D11/D13 1N4148 1N4148... -
Page 55: Transistors
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 9.20 T RANSISTORS Circuit Reference Issue 4a, 4b, 5, 6a TR1-TR2 ZTX313/MPS2369/MPS2713/KSC945-Y ZTX313/MPS2369/MPS2713/KSC839-0 2 and 6 ZTX650/TIPP31/KTC2236A-7 ZTX231/BC213/BX214/FRB925 ZTX313/MPS2369/MPS2713 ZTX450 TR8/TR9 BC184/BC549B 9.21 M ISCELLANEOUS Reference Description Manufacturer/Part Number 5V regulator... -
Page 56: Supplement No 2
NTRODUCTION The ZX Spectrum+ is basically the same as the 48k ZX Spectrum with a different keyboard and case, and a reset button. The board circuitry is similar apart from the reset button and the fitment of an extra resistor. -
Page 57: Assembly Of The Keyboard For The Spectrum
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ 10.3 A SSEMBLY OF THE EYBOARD FOR THE PECTRUM The flextails running from the keyboard to the clamps should lie in an S shape, to prevent tension in the membrane. This is achieved by ensuring that the end of the tracks on the middle layer protrude by 1mm past the clamps. -
Page 58: Spectrum + Keyboard - Top Membrane
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ Also pressing any one of the following keys also makes contact between row 2 and column 8 on the top membrane in addition to their dedicated row/column positions. . (full stop) ;... -
Page 59: Spectrum+ Keyboard - Lower Membrane
Sinclair ZX Spectrum Service Manual Spectrum For Everyone https://spectrumforeveryone.com/ – L 10.6 PECTRUM EYBOARD OWER EMBRANE...