Spectrum, Timex, Sam keyboard upgrade
Foil membrane - ZX Spectrum
The original ZX Spectrum keyboard membrane life was several years. So replacements were developed.
Membrane clones were produced in Poland by QWERTY (£ód¼) and KEYPOL (Zielona Góra). Still are in their offer, however not cheap.
If the case was open many times, the ends of belts got damaged. To prevent the damage, an angled male pinheads can be soldered to the board, and female pinheads must be soldered to the flat belt connectors.
Many years ago, in Bajtek were published an article about keyboard made from cardboard and wire. It could be done at almost no cost and could work some months, until the cardboard got borken. However, this solution wasn't suitable for ZX Spectrum + with extra keys (over the basic 40).
Printed circuit board
The solution intermediate in cost is to use one-side coppered laminate and steel wire. Then both are used as in the cardboard idea.
In case of ZX Spectrum +, the extra keys can be supported with simple logic. 4 AND gates generate signals to drive the extra keys matrix. Then lines A8, A11, A12, A13, A15 and 5 outputs from the extra keys matrix go to 1kB EPROM. Outputs of EPROM go as open collector to ULA keyboard inputs. Of course the chips must be powered, what requires two more wires.
Files for download
- zxplus128k.jpg 113.4kB (2007-03-21 21:55), uploaded by ArturGrutz
- Foil keyboard like ZX81 for ZX+, based on ZX48 foil from Keypol. On the back is TI-of-TTL with custom case connected to PC.
- external.jpg 53.6kB (2005-09-15 02:06)
- External keyboard for ZX Spectrum+, made in 1999 by Jarek Adamski.
- 59528526.jpg 48.3kB (2005-08-04 13:56)
- ZX Spectrum mebrane by QWERTY. Picture taken from auction.
Links to other pages
- "KEYPOL" - Producent klawiatur membranowych
- Klawiatury foliowe, klawiatury membranowe - "QWERTY" Sp. z o.o.