So, I took Bill up on the offer of a Spectrum clone PCB. I know he want's some updates, so I've posted a couple of pictures.
While I wait for the rest of the parts to arrive in post from the US, I've started on the keyboard.
I used the 48k spectrum as a guide, since there's no way to duplicate the "key and shift" double keypress of the 128 and later Spectrums with the key-switches I have to hand. Sinclair seem to have used a 20mm spacing, so the matrix board's best fit of 8 holes is 20.32mm is close enough. The depth of the board is sufficient to put the space in it's proper place. I thought about duplicating the shift keys on both sides, but decided on the end to just double them up to make them wider, but keep the original positions.
The keys are now all in place, waiting for some wiring, but this is how it fits over the PCB. I used slightly longer than required posts to make sure there's clearance for the cables that will connect the keyboard, and the AY-3-8910 to 8912 adaptor board I'll also need to squeeze in between the boards to get the sound working.
PS Have you seen the cost of the AD724JR AD converter chip ? It's more than the Z80, a lot more!