Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
2
CONTENTS
1 System Description .................................................................................................................................... 4
1.1 Introduction ........................................................................................................................................ 4
1.2 Architecture ........................................................................................................................................ 5
1.3 Z80A CPU ............................................................................................................................................. 5
1.4 Memory Organisation ......................................................................................................................... 7
1.4.1 Read/Write Operations and Bus Arbitration ............................................................................... 8
1.5 Input/Output ..................................................................................................................................... 11
1.5.1 TV Picture Generation and Sound Output ................................................................................. 11
1.5.2 Keyboard Scanning ..................................................................................................................... 12
1.6 Tape Interface ................................................................................................................................... 15
1.6.1 ULA Sound Output ..................................................................................................................... 15
1.7 Programmable Sound Generator ...................................................................................................... 16
1.8 RS232/Midi Interface ........................................................................................................................ 17
1.9 Keypad Scanning ............................................................................................................................... 17
1.9.1 Reset Protocol ............................................................................................................................ 18
1.9.2 Bit Transfer Protocol .................................................................................................................. 19
1.10 Power Supplies ................................................................................................................................ 20
2 Disassembly/Assembly ............................................................................................................................. 22
2.1 Disassembly ....................................................................................................................................... 22
2.2 Assembly ........................................................................................................................................... 22
3 Setting Up and System Test ..................................................................................................................... 24
3.1 Setting Up Instructions ..................................................................................................................... 24
3.2 System Test ....................................................................................................................................... 24
4 Fault Finding and Repair .......................................................................................................................... 25
4.1 Introduction ...................................................................................................................................... 25
4.1.1 Test Equipment .......................................................................................................................... 25
4.2 Fault Diagnosis .................................................................................................................................. 27
4.2.1 Techniques ................................................................................................................................. 27
4.2.2 Power Supply Unit ...................................................................................................................... 27
4.2.3 Initialisation ................................................................................................................................ 27
4.2.4 Symptomatic Faults .................................................................................................................... 29