Sinclair ZX Spectrum Service Manual

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
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5.4.1 Example
If a 48k Spectrum is giving a memory of 25.25k key in the following instruction:
PRINT PEEK 23732+PEEK 23733*256
Assume the answer displayed is 43200, therefore the faulty location is 43201 (stops at last valid location).
Key-in:
POKE 43201,85: PRINT PEEK 43201 (=answer A)
If answer A is 85, key-in:
POKE 43201,170: PRINT PEEK 43201 (=answer B)
If answer B is anything other than 170 look up in following table which IC to change (e.g. if answer B is 234
change IC21). Similarly, if answer A is other than 85 refer to the table to find the faulty IC.
Data 85
IC6 – IC13
Data 170
IC15-Ic22
Size of Error
Error Bit
Faulty RAM
location if <
32768
Faulty RAM
location if >
32767
84
171
1
0
IC6
IC15
87
168
2
1
IC7
IC16
81
174
4
2
IC8
IC17
93
162
8
3
IC9
IC18
69
186
16
4
IC10
IC19
117
138
32
5
IC11
IC20
21
234
64
6
IC12
IC21
213
42
128
7
IC13
IC22
If there is more than one faulty RAM location the first fault identified will have to be repaired before it is
possible to proceed.

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)