Sinclair ZX Spectrum Service Manual

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
36
7 FAULT DIAGNOSIS AND REPAIR – COLOUR, REPAIR AND UPGRADES
IC14 (LM1889) Pin Signals
Repair
16k to 48k Upgrade
Integrated Circuits/Link Settings
Issue 2 Board
Issue 3 Board
7.1 IC14 (LM1889) PIN SIGNALS
Pin No.
Signal
1
(Chroma lead) Sinewave 500mV, 0.2us, DC 9.5V
2
(R-Y Input)
3
(Chroma Bias) 4.8V DC
4
(B-Y Input)
5
(Ground) 0V
12
(Video input) DC 12V unregulated
13
(Chroma subcarrier)
14
(RF Supply)
15
(Sound tank) ‘Linked’ 12V DC
16
(Chroma supply)
17
(Chroma oscillator output) Square wave 0.2us 4V p-p 0.8V DC
18
(Chroma lag) Sine wave 500mV p-p 2us 9.5V DC
6,7,8,9,10,11
Not connected

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)