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Sinclair ZX Spectrum Service Manual
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Sinclair Z
X Spectrum Service
Manual
Spectrum For Eve
ryone
https://spe
ctrumforev
eryone.com/
36
7
F
AU
LT
D
IA
GNO
SIS
AN
D
R
EP
AIR
–
C
OLO
UR
,
R
EP
AIR A
ND
U
PG
RA
DE
S
IC14 (LM1
889) Pin Signal
s
Repair
16
k t
o 48k Upgrade
Integrated Cir
cuits/Link Setting
s
Issue 2 Boa
rd
Issue 3 Boa
rd
7.1
IC1
4
(L
M
18
89)
P
IN
S
IG
NAL
S
Pin No.
Signal
1
(Chroma lead) Sinewa
ve 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 1
2V unregulated
13
(Chroma subcarri
er)
14
(RF Supply)
15
(Sound tank) ‘Link
ed’ 12V DC
16
(Chroma supply)
17
(Chroma oscillator
output) Square wave
0.2us 4V p-p 0.8V DC
18
(Chroma lag) Sine wa
ve 500mV
p-p 2us 9.5V DC
6,7,8,9,10,11
Not connected
35
37
Table of Contents
Default Chapter
2
Table of Contents
2
1 Introduction
7
Architecture
8
Z80A Cpu
8
Data Bus
8
Address Bus
8
Control Bus
8
CPU Clock
9
Dynamic Memory Refresh
9
Memory Organisation
9
Read/Write Operations
10
Read Only Memory (IC5)
10
Standard 16K RAM (IC6-IC13)
10
Expansion RAM (IC15-IC32)
11
Input/Output
13
TV Picture Generation
13
Keyboard Scanning
14
Tape Interface
15
Loudspeaker (BEEP) Operation
15
Power Supplies
15
2 Disassembly/Assembly
16
Disassembly
16
Assembly
16
3 Setting up and System Test
17
General Alignment
17
Introduction
17
Voltage Check
17
Colour Adjustment
18
Sub-Carrier Oscillator
18
14 Mhz Oscillator
18
System Test
19
4 Fault Diagnosis and Repair - Getting Started
20
Introduction
20
Test Equipment
20
Modification History
21
Modifications - Issue 1 Board
22
Modifications - Issue 2 Board
23
Modifications - Issue 3B Board
23
Extension Memory - (16K to 48K)
23
Board Issue 1
23
Board Issue 2
23
Board Issue 3
24
Hitachi Vs NEC ROM
24
5 Fault Diagnosis and Repair - PSU and Memory
25
Fault Diagnosis Techniques
25
Power Supply Unit
25
Initialization
26
Basic Checks
26
Memory Check
27
Example
28
Keyboard Structure
29
6 Fault Diagnosis and Repair - Input/Output
30
TV Screen Dead, Smoke Appears on Switch-On / Not Initialising
30
TR4 Base-Collector Shorted
30
Short Persists with TR4 Removed
30
TR4 Blows Again
30
No Video
31
No Video after ULA Changed
31
No +5V Input
31
No VIDEO INPUT at IC14 Pin 12
31
Corrupt Paper, after ULA Change
32
Initial Check
32
No 3Mhz at IC2 Pin 6
32
Distorted Video
33
Pin Screen
34
Speaker
35
7 Fault Diagnosis and Repair - Colour, Repair and Upgrades
36
IC14 (LM1889) Pin Signals
36
16K to 48K Upgrade
36
Repair
37
Integrated Circuits/Link Settings
37
Issue 2 Board
37
Issue 3 Board
38
Issue 3 Links Vs IC Manufacturer and Type
39
Expansion Memory IC Locations
40
8 Parts List
41
Introduction
41
Notes to Parts List
41
General Capacitor Change
42
Case Assembly
42
Capacitors - All Axial Types Unless Otherwise Stated
43
Coil
44
Connectors
44
Crystals
44
Diodes
44
Integrated Circuits
44
Resistors - All 1/4W, 5% Unless Otherwise Stated
45
Transistors
46
Miscellaneous
46
9 Supplement No. 1
47
Introduction
48
DC-DC Converter Modification
48
Circuit Operation
49
Issue 3B Board - (Already Covered in Existing Manual)
49
Issue 4 Board - None Issued
49
Issue 4A Board
49
Issue 4B Board
49
Issue 5 Board
49
Issue 6 Board - None Issued
50
Issue 6A Board
50
Fault Finding - Servicing Addenda
50
Warranty Seal
50
Parts Lists
50
Notes
50
Capacitors - Unless Otherwise Stated All Are Axial Types
51
Coil
52
Connectors
52
Crystals
52
Resistors - 0.25W, 5% Tolerance Unless Otherwise Stated
53
Diodes
54
Integrated Circuits
54
Transistors
55
Miscellaneous
55
10 Supplement no 2
56
Introduction
56
Conversion Procedure - Spectrum to Spectrum
56
Assembly of the Keyboard for the Spectrum
57
Keyboard Operation
57
Spectrum + Keyboard - Top Membrane
58
Spectrum+ Keyboard - Lower Membrane
59
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Sinclair ZX Spectrum Specifications
General
Brand
Sinclair
Model
ZX Spectrum
Category
Desktop
Language
English
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