Sinclair ZX Spectrum Service Manual

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
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4.5.3 Board Issue 3:
This allows OKI ICs to be used in place of TI 4532. Again, all ICs must be of the same designation.
Appropriate links (2) must be fitted in the grid located on the board between the edge connector and the
`mic` jack socket. Again, the extra memory is obtained by plugging in 4 logic ICs and eight memory ICs.
4.6 HITACHI VS NEC ROM
During manufacture, wiring links are selected and inserted in the board according to whether a Hitachi or
NEC ROM is used. These links are marked `H` and `N` as appropriate and are located as follows:
• Board Issue 1 - between the ROM and the heatsink
• Board Issue 2 - beneath the raised portion of the heatsink
• Board Issue 3 - adjacent to the loudspeaker
Clearly, if the ROM is changed for one of a different make, then these links must be changed as well.

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)