of Sinclair's products were produced in the form of self-assembly
kits. Something of that spirit survived well into the 1980s,
in the shape of do-it-yourself upgrade kits for the ZX computers.
The difference between the
was not actually that great, as both machines had very similar
hardware - the major differences were the keyboard and the
ROM chip. Both could readily be upgraded with the use of a
simple do-it-yourself kit which Sinclair produced, consisting
of a ZX81 ROM and keyboard overlay (above). Replacing
the existing ROM and keyboard was a straightforward task.
16K to 48K
Spectrum originally came in two versions, identical
in every way except in memory capacity. It very quickly became
clear that the 48K Spectrum was the more popular model. Sinclair
responded by offering a memory upgrade for £60, which
required the computer to be returned to the company for the
new memory to be fitted. Initially the design of the first
(Issue 1) version of the Spectrum motherboard required the
extra memory to be added on a rather inelegant daughter board
(above). Later on, a redesigned motherboard permitted
the chips to be added directly onto the board.
16/48K to Spectrum+
introduced in 1984, was literally no more than a conventional
Spectrum 48K in a new box with a supposedly "professional"
typwriter-style keyboard (although actually it used the familiar
rubber membrane). As such, converting an existing Spectrum
16K or 48K into a Spectrum+ was very simple - it required
no more than transferring the motherboard into the new case.
Sinclair Research offered a simple do-it-yourself upgrade
kit for £20, or offered to do the job themselves for
© Chris Owen 1994-2003