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Many 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.

ZX80 to ZX81

The difference between the ZX80 and ZX81 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.

Spectrum 16K to 48K

The ZX 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.

Spectrum 16/48K to Spectrum+

The 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 £30.

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Chris Owen 1994-2003