Friday, 28 June 2013

USB Keyboards for sale

I've written a number of articles in the past about USB keyboards I've built from broken Sinclair ZX81's and  other old 8-bit home computers. I've had many requests since starting those articles to build keyboards for blog readers, and have build quite a few. Most of the ones I've been able to do were along the lines of 'can I send you my old X to turn into a USB keyboard'. The difficult ones have been, can you sell me an X USB keyboard. The difficulty being finding suitable source machines, when I try to stick to a policy of only using broken machine. One thing on my side is almost all of these machines have an Achilles heel, one or more custom chips. These ULA (Uncommitted Logic Array) or PLA (Programmable Logic Array) and similar chips were the ancestors of todays CPLDs and FPGAs and  were cost and complexity reduction exercises in the 1980's which allowed the ZX81 for example to be considerably smaller than the ZX80.
The size reduction was almost all due to combining multiple logic chips into a single chip. The problem with that is the chips were custom made, and no longer available. They also had a tendency to run hot and overheat. If you're looking at an Acorn Electron, a Spectrum, a ZX81 or a Commodore 64 or anything from that era that isn't running, the first things to check is the ULA or PLA. Sometimes (particularaly with Electrons), they just need clearning and reseating, but more often than not, they have gone to silicon heaven.
Unfortunately, these days the only source for a replacement ZX81 ULA is another ZX81. There are projects to build replacements, some are exact replacements, some approximate, and some add useful new feature. However, without those, you can end up with redundant machines. I normally wait until I've got something with multiple faults, so it really isn't going to come back to life, duff memory or CPU, the ULA has been passed onto another machine, etc. Or as happens with a depressing number of Commodore units, the poorly designed PSU has failed and shot 9V across the 5V rail and fried all the chips.
I picked up a number of units from ebay. I went for things advertised as 'not working', or in ebay speak 'untested' - which normally means 'I plugged it in and the light didn't come on' (as opposed to 'fully tested' which means 'I plugged it in and the light did come on'). However, I was disappointed to find a number of these actually worked or were easily reperable, so these ended up in my spares pile and I continued the search for broken units.
I have now amassed a selection of suitable computers and built up some USB keyboards, so I have setup the Tynemouth Software Etsy Store, and all the machines shown below are available to buy now. Alternatively, contact me for further information or if you have an old computer you would like turned into a USB keyboard.
The range for sale includes two Commodore 64's, one original and one C64C, although the keyboard of the C64C has been replaced by an older C64 version.
There are two Sinclair ZX Spectrums, an original rubber key version:
and a later ZX Spectrum Plus version with the better keyboard.
There is an Acorn Electron:
And, finally, a Sinclair ZX81, like the one that started this whole thing off:
All of these will work just like a normal USB keyboard, just plug and go. Windows XP / Vista / 7 and 8 are supported as are Mac and all flavours of Linux, including those running on a Raspberry Pi. Also, any tablets that support normal USB keyboards. They keyboard mappings can be customised at build time as required for any particular keys not included in the standard layouts. These are now available to buy now at the Tynemouth Software Etsy Store. Contact me for further information or requests.
Note also, most of these (barring the Spectrums) have space to install something like a Raspberry Pi inside (Pi and USB hub not included).