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This is the ZX Max 48, a Sinclair ZX Spectrum 48K clone by Superfo (who also designed the Harlequin). Real Z80, ROM and RAM, and all the logic of the ULA in a CPLD.
ZX80 style overlays I do for my Minstrel ZX80 clones. He kindly sent a PCB and CPLD so I could build one.
my Tindie store).
r you can get the overlays and ZX81 membranes from my Tindie store).
Harlequin board I repaired. That had a dodgy 74HC04 chip. I tried a few others here, including the unbuffered version, the 74HCU04 (as used on the Spectrum +2). That didn't help, so I wasn't sure what the issue was. Might have been something up with the crystals I bought. I looked at other series resonant oscillators, and the capacitor value was generally larger, so I swapped out the 100pF for 100nF on the 4.43MHz side and it came to life.