Sinclair ZX Spectrum Service Manual

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
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CONTENTS
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 ..................................................................................................................................... 9
1.3.5 Dynamic Memory Refresh ........................................................................................................... 9
1.4 Memory Organisation ......................................................................................................................... 9
1.5 Read/Write Operations ..................................................................................................................... 10
1.5.1 Read Only Memory (IC5) ............................................................................................................ 10
1.5.2 Standard 16k RAM (IC6-IC13) .................................................................................................... 10
1.5.3 32k Expansion RAM (IC15-IC32) ................................................................................................. 11
1.6 Input/Output ..................................................................................................................................... 13
1.7 TV Picture Generation ....................................................................................................................... 13
1.8 Keyboard Scanning ............................................................................................................................ 14
1.9 Tape Interface ................................................................................................................................... 15
1.10 Loudspeaker (BEEP) Operation ....................................................................................................... 15
1.11 Power Supplies ................................................................................................................................ 15
2 Disassembly/assembly ............................................................................................................................. 16
2.1 Disassembly ....................................................................................................................................... 16
2.2 Assembly ........................................................................................................................................... 16
3 Setting Up and System Test ..................................................................................................................... 17
3.1 General Alignment ............................................................................................................................ 17
3.1.1 Introduction ............................................................................................................................... 17
3.1.2 Voltage Check............................................................................................................................. 17
3.1.3 Colour Adjustment ..................................................................................................................... 18
3.1.4 Sub-Carrier Oscillator ................................................................................................................. 18
3.1.5 14 MHz Oscillator ....................................................................................................................... 18
3.2 System Test ....................................................................................................................................... 19

Sinclair ZX Spectrum Specifications

General

Processor	Zilog Z80A
Clock Speed	3.5 MHz
RAM	16KB or 48KB
ROM	16KB
Graphics	256 x 192 resolution
Sound	1-channel beeper
Storage	Cassette tape
Input	Keyboard
Power	9V DC
Release Year	1982
Display	TV via RF modulator
Ports	Expansion, RF
Colors	15 (8 colours with two levels of brightness each, plus black)