Sinclair ZX Spectrum Service Manual

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
37
Notes:
Rails and signals taken on switch-on, computer displaying `Sinclair` logo.
No keys pressed
All DC levels positive with respect to 0V
7.2 REPAIR
Renewal of components should be carried out using recognised desoldering/heatsinking techniques to
prevent damage to the component or to the printed circuit board. Other points to be noted are:
• When replacing a keyboard matrix, take care that the ribbon connectors are fully inserted into
the board connectors, and are not kinked during insertion.
• Make sure there is a good contact made between the voltage regulator body and the associated
heatsink in order to ensure adequate heat conduction. The heatsink hole in certain Issue 3 boards
allows excessive play which could cause fouling of the edge connector. Take care in re-assembly
that the heatsink is fitted away from the edge connector.
• When the regulator is being replaced it is recommended that a suitable proprietary thermal
grease is applied to the rear surface of the component body.
• The modulator should be replaced as a complete unit.
• When replacing plug-in ICs it is advisable to use the correct removal and insertion tools. Avoid
contaminating the connection pins by handling.
• When handling ICs take normal anti-static precautions. It is recommended that only a suitably
earthed, low power soldering iron be used.
• After any component has been renewed the circuit board should be examined carefully, to ensure
that there are no solder ‘splatters’ which may cause short circuits between tracks or connector
pins.
7.3 16K TO 48K UPGRADE
7.3.1 Integrated Circuits/Link Settings
For both the Issue 2 and the Issue 3 boards the memory upgrade is accomplished by plugging four logic
ICs and eight memory ICs into existing board sockets. Depending on the types of memory ICs used,
appropriate circuit links must be fitted on the board.
7.3.2 Issue 2 Board
The ICs used on this board are as follows:
IC
Type
IC15-IC22
TI 4532-3 or TI 4532-4 200ns (or 250ns)
IC23
74LS32
IC24
74LS00
IC25, IC26
74LS157 (NOT National Semiconductors)

Sinclair ZX Spectrum Specifications

General

Brand	Sinclair
Model	ZX Spectrum
Category	Desktop
Language	English