Sinclair ZX Spectrum

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
2
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