This is a keyboard designed for use with the ZX Spectrum Harlequin boards. The design of the Harlequin Spectrum replaces the troublesome ULA with 74HC logic, the DRAMS have been replaced with CMOS static RAM and the ROM has been replaced with a CMOS EPROM. This means that the Harlequin Rev G no longer requires the buck converter circuit to generate the additional supply rails required by the DRAMS and runs at a much lower current. I have had a Harlequin board running from a single 18650 (with a buck boost circuit to boost the 3.7V(Nom) to around 7.5V). This keyboard will also work with old Spectrum 16/48k machines. The buttons used are cheap tactile buttons found on eBay and Aliexpress.

Update 27/05/24: Just uploaded a zipped KiCad project folder with a 1:1 printable key top legends design.

I have the Gerber files for the Harlequin Rev G board. I believe they're in the public domain and I may upload them soon. The Gerbers can be found on the web and readymade PCBs can be ordered from several places online, including eBay.

https://www.ebay.co.uk/itm/223494111694 - (Square through hole type)