Module replace the eight 4532 or equivalent chips form the upper 32Kb of RAM in a 48K ZX-Spectrum computer issue 2 or later. Or upgrade a 16K ZX-Spectrum to a 48K. The upper RAM needs IC23, IC24, IC25 and IC26 chips.
If 16K ZX-Spectrum,
support logic for the upper RAM must be
installed. On earlier boards these chips mark IC23, IC24, IC25 and IC26. On
later boards issue 6 this logic is contained in a single 40-pin chip IC27.
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 4532 or equivalent chips (IC15-IC22),
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 pin 1
indicator to orientate it of IC socket IC22 (the top left pin) and that the
board is mounted squarely so that all the other pins are aligned correctly, 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 upper 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.
Jumper links
The jumper
links settings should be installed for this PCB module, valid configuration
should still be set:
Issue 2
board - on the top right of IC1 (ULA chip) there are 3 pads, the top is marked +5v,
the bottom is marked 0v. The upper pad
must be connected to the central one.
Issue 3-6 boards - on the right of the MIC socket, under the heatsink, there are two groups of pads marked TI and OKI, must be connected TI linked and OKI 3
All modules undergo pre-sale testing on a real computer with a long memory test.
Read unstallation manual on retro-spektro site
LOT - 1pcs 32K Upper RAM Replacement Module.