Sinclair ZX Spectrum Service Manual 
Spectrum For Everyone  https://spectrumforeveryone.com/ 
20 
4 FAULT DIAGNOSIS AND REPAIR – GETTING STARTED 
 
 Introduction 
 Test Equipment 
 Modification History 
 Modifications - Issue 1 Board 
 Modifications - Issue 2 Board 
 32k Extension Memory - (16k-48k) 
 Hitachi vs NEC ROM 
 
4.1 INTRODUCTION 
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. 
Specification/Manufacturer 
Oscilloscope with oscilloscope probe (x10) 
Variable power supply unit 
With RECORD and PLAYBACK facilities 
Double-sided adhesive tape 
12mm and 6mm wide, Tesafix 959 (BDF TESA), or 
3M equivalent 
 
Engineers who are already familiar with the Sinclair ZX81 will find some similarities in the ZX Spectrum. 
The Spectrum, however, is a more sophisticated device with colour and sound circuitry. 
The ZX Spectrum is supplied with either 16k or 48k of on-board RAM. The 16k version is wired so that it 
can be expanded to 48k by the addition of a number of appropriate plug-in ICs. For details of the memory 
upgrade, see section 7.3.