View Full Version : Help: ZX Spectrum external keyboard

August 31st, 2008, 04:04 AM
I picked up this keyboard at the flea market today. It was being sold together with a Speccy, psu and cables but I only wanted the keyboard. I didn't bother with examining the Speccy but I probably blew it for only getting the keyboard itself. Anyone familiar with this model? Were there additional cables supplied that connect directly into the on-board keyboard connectors? The blue connector looks exactly the same as Speccy's edge connector which is weird, if it wasn't meant to be connected directly to it. Find attached some photos.


http://shrani.si/t/2y/eU/2J7HzMbU/keyboardkbd.jpg (http://shrani.si/?2y/eU/2J7HzMbU/keyboardkbd.jpg) http://shrani.si/t/M/PH/XTeUIWq/keyboardback.jpg (http://shrani.si/?M/PH/XTeUIWq/keyboardback.jpg) http://shrani.si/t/3Z/yk/3PZhEwYs/keyboardkeys.jpg (http://shrani.si/?3Z/yk/3PZhEwYs/keyboardkeys.jpg) http://shrani.si/t/N/c9/9RLVwFU/keyboardconnector.jpg (http://shrani.si/?N/c9/9RLVwFU/keyboardconnector.jpg)

August 31st, 2008, 06:55 AM
I can't answer the question, but that is a beautiful keyboard. My Timex Sinclair 1000 (ZX81 clone) suffered from the bad keyboard ribbon connector too, making it unusuable. Eventually I will pick it up, but the first thing I'll have to do is replace the keyboard/ribbon cable combination.

I doubt that it is an external keyboard. It is more probable that the main cpu was being used to read the keyboard matrix. If you were to disconnect the standard keyboard you could probably access the same bus pins needed for the keyboard on the bus connector. If that connector you have provides passthrough for another device it would make this theory more plausible.

August 31st, 2008, 07:52 AM
Thanks Mike. In reply to your question, there's only one connector (blue one) at the end of the flat cable. The shematics are a bit enigmatic for me as it could mean that you have to use two separate flat cables from the blue edge connector to the motherboard. Again, I'm unsure of this. The instructions clearly say that you have to disconnect the original keyboard. Maybe I'll try this later this week, when I have more time.


P.S. Inside the black box with the blue connector there are 2 or 3 chips (unknown, probably TTL gate arrays) and some resistors.

August 31st, 2008, 10:13 AM
I tried to locate a pinout of the expansion bus, but it seems very hard to find even after several minutes of qualified Google-time. Finally I found one document in Spanish (!) describing the bus:

Exactly which signals do what, I can't tell but it may be possible to override the keyboard from the expansion bus although the keyboard clearly says you should do internal modifications to make it work.

August 31st, 2008, 12:02 PM
I also checked an old ZX Spectrum repair book at home and it would seem that the keyboard doesn't have any direct connection to the edge connector.

Does anyone here have an idea where to get suitable flat connectors for the motherboard?


September 2nd, 2008, 10:41 AM
The assembled keyboard looks like this:
http://shrani.si/t/3f/6C/4hqm0hZl/keyboardcomplete.jpg (http://shrani.si/?3f/6C/4hqm0hZl/keyboardcomplete.jpg)

November 20th, 2008, 05:24 AM
There are no keyboard connectors as such. The sinclair computers have the keyboard attached to the address and data lines of the CPU. These are brought out on the edge connector, and so external keyboard interfaces fit there. No software drivers are needed, just plug and go.

See here:

and here: