Sinclair ZX Spectrum Service Manual

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
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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 (ie 10ppm absolute,
10ppm 20C to 60C, 5ppm per year.)
7. On Issue 3B boards, the dc converter design has improved reliability. R60 is changed from 270R
to 68R and C49 is changed from 47nF to 560pF. Capacitor C77 (100nF) has been added.
8.3 GENERAL CAPACITOR CHANGE
Early Issue 2 units were manufactured using a considerable number of 47nF and 100nF disc capacitors.
Where these occur, the service engineer should take the opportunity to replace C41 and C49 with axial
types.
8.4 CASE ASSEMBLY
Description
Manufacturer
Assembled board as appropriate
Moulded Upper Case
Moulded Lower Case
Keyboard Mat (Rubber)
Keyboard Membrane
NFI
Keyboard Template
Rubber Feet
Self Tapping Screws (case fixings), 5 off
Double-sided adhesive tape – 12mm wide; Tesafix 959
BDF Tesa
Double-sided adhesive tape – 6mm wide; Tesafix 959
BDF Tesa
Self Tapping Screw (board fixing), 1 off

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)