What is it? This is a PCB which can be used to build a ZX80 clone. An 8bit Z80 based computer, the predecessor of the ZX81 and ZX Spectrum. It has 4K or 8K of ROM, 16K of RAM and a 3.25MHz Z80 Processor. Input is via an 8x5 matrix keyboard (not included - see below for options), output via composite video (improved over the original ZX80 design). It is programmed in a simple version of BASIC. 10 PRINT "HELLO WORLD", 20 GOTO 10, RUN.
Why did you make it? The ZX80 itself is quite rare, this is an easy way to build a version with modern parts which is fully ZX80 compatible.
What makes it special? It is built in the form factor of the ZX81, so can be used as a replacement board for a broken ZX81. The design follows the original ZX80 design with only a few changes. The RAM has been upgraded to 16K, and the ROM socket can take a 2764-27512 EPROM with 1 to 8 ROM images which are jumper selectable. The video output has been improved and is now a composite video signal rather than the version generated by the original ZX80 and early ZX81 boards which were missing one part which affected the black level on modern TVs.
All parts are through hole, so assembly should be straightforward. It can be used with the original ZX80 4K BASIC ROM or the later ZX81 like 8K BASIC ROM. Note these issue 2 boards do not have the NMI based slow mode, so are not fully ZX81 compatible.
What options are available? This is available as a bare PCB or as a kit of parts to build the main board. The kit does not include a keyboard or case.
IC Sockets The standard kit comes with turned pin IC sockets for the CPU, ROM and RAM. You can optionally add sockets for all the other ICs on the board.
Voltage Regulator If you are fitting this into a ZX81 case, you can select a 7805 regulator and reuse the ZX81 heatsink. In most cases, go for the switch mode replacement (small black box which is more efficient and does not require a heatsink).
PCB Colour The standard PCB is green. I have a limited supply of blue versions of the PCB which match the RC2014 keyboard.
Keyboard Connector You can fit various 8x5 matrix keyboards to the Minstrel. Select the appropriate connectors based on the keyboard you plan to use.
Base Plate I can supply a clear perspex base plate as shown in the third picture to mount the Minstrel and a ZX80-KDLX keyboard, RC2014 keyboard or ZX81 membrane (none included). Comes with drilled perspex sheet and nylon pillars and screws. The RC2014 version has 4 additional hole and fixings to mount the keyboard. The others are stuck to the perspex.
Builds If you want to build one like the third picture, a ZX80 clone, select switching regulator, ZX80-KDLX connector and base plate. If you want to build a board to fit into a ZX81 case, select 7805 regulator and ZX81 membrane. Sockets are up to you.
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