Module used to replace the eight 4116 ICs from the lower 16K of RAM in a 16K or 48K ZX-Spectrum computer. For Issue 2, 3, 3B, 4A, 4B, 4S, 5, 6A.
As you know, memory chips for old computers have not been produced for a long time, the quality of the chips themselves leaves much to be desired, they often fail due to time or power supply problems. The module uses a modern low power CMOS technology SRAM memory chip.
To install the module, you need to: disassemble the computer, carefully disconnect the keyboard cables, unscrew the central screw holding the main board and remove it from the case. Desolder all eight 4116 chips (IC6-IC13), carefully check all connections and tracks, because there is a risk of damage if you unsolder carelessly. Install eight standard 16-pin DIL panels, please note that collet (round pins) panels are not suitable for this replacement board.
WARNING: The module mounting pins may be sharp, take care when handling it. Observe static precautions when installing the module and store it in an anti-static bag until installation. CMOS type components that are easily damaged by static electricity.
The pins should be perfectly perpendicular to the lower surface of the module circuit board.
The module should be aligned squarely over the row of DIL sockets, using the TOP indicator to orientate it when viewing the ZX-Spectrum PCB from above and the front.
Then slowly and evenly press the module into the sockets. Press down on the module circuit board rather than its components.
When installing the module, take care to make sure that all its pins are properly inserted into the correct socket contacts.
Alternatively the lower RAM module can be soldered directly to the ZX-Spectrum PCB without the use sockets. In this case, it is necessary to make a gap of two millimeters from the ZX-Spectrum board.
Place the ZX-Spectrum PCB back into the case. Power up, you can test the computer without the keyboard membrane attached. Computer should boots to the copyright screen, disconnect the power and proceed with assembly. Push the membrane tails back into their sockets, place the top section of the case.
The lower RAM module uses only 5V power supply does not need the 12v and -5v supplies the ZX-Spectrum. However, you should make sure the ZX-Spectrum DC-DC converter circuit is working.
It is recommended to install impulse voltage converter instead of the 7805 stabilizer, which will reduce heating, allow you to get rid of the aluminum radiator and extend the life of the keyboard membrane.