Sinclair ZX Spectrum

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
28
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.