Sinclair Research ZX Spectrum - ZX Spectrum Parts List; Introduction to Parts Lists

SECTION 5
PARTS LIST
Sub-Section LIST OF CONTENTS Page No.
1 Introduction 5.1
2 Notes to Table 5.2 5.1
1. INTRODUCTION
1.1 Parts lists for the ZX SPECTRUM are provided in table form; one for
the case assembly (Table 5.1) and another for the board assembly
(Table 5.2). The latter covers the Issue 2 and 3 Spectrums and is
related to the board layout diagrams given in Figure 5.1 and 5.2.
Table 5.2 also lists the alternative components which the service
engineer will occasionally find on production versions of the Issue 2
board or may introduce retrospectively in order to improve
performance. These components are listed in the column headed 'ISSUE
2 MODS' with references to notes against them. These notes are
explained below-
2. NOTES TO TABLE 5.2
(1) The alternative values given for R47, R49, R56 and T63 are used
if the ULA fitted is Type 6C001.
(2) The alternative values for R48, R50, R72 and C65 are introduced
to improve the colour quality.
(3) C74 is essential on all Issue 2 boards and should be fitted
retrospectively. At the same time R60 must be replaced with the
larger value.
(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).
(6) On Issue 3 boards only crystal X2 must have a close tolerance
specification (i.e. 10 ppm absolute, 10 ppm 20°C to 60°C, 5 ppm
per year.)
(7) On Issue 3B boards, the d.c. converter design has improved
reliability. R60 is changed from 270n to 68ft and C49 is changed
from 47nF to 560pF. Capacitor C77 (lOOnF) has been added.
5.1