Time to go back in time again - ZX80 replica build

[rubber_jonnie]

I was going to put a Traco voltage regulator in it, though I do have lots of spare 7805's if I can't find one.

The TRACO would be a good choice.

And is now installed

[HigashiJun]

@rubber_jonnie

Nice move !

[rubber_jonnie]

@rubber_jonnie

Nice move !

Just did a smoke test and no smoke
9v into the Traco and 5v at the sockets so all looking good I can start installing IC's now.

[HigashiJun]

I can start installing IC's now.

And 1 or 2 days later:

Franken.gif (173.74 KiB) Viewed 119 times

[stephen_usher]

The ony issue with buck converters vs. regulators is that the former can produce a lot of high frequency noise. Not that this should affect a ZX80 clone much given how noisy they are.

[rubber_jonnie]

I can start installing IC's now.

And 1 or 2 days later:


Franken.gif

[rubber_jonnie]

The ony issue with buck converters vs. regulators is that the former can produce a lot of high frequency noise. Not that this should affect a ZX80 clone much given how noisy they are.

I'm using the same Traco's in my real Spectrums and also my MK14 replica. so far no problems, but yes they can be a problem for sure, though the Traco's seem to be quite good in that respect.

There was a very good video comparison of various Traco and similar 7805 replacements, if I have time I'll go and look for the link.

[rubber_jonnie]

Not entirely sure why the 74LS93 has VCC & GND in different positions (Pins 5&10) to just about every other 74LS IC out there...

Annoying.

[rubber_jonnie]

Small update over lunchtime, most ICs are now installed:

IMG20250915125726.jpg (344.44 KiB) Viewed 99 times

And I've done another smoke test which was just fine. Just pending the remainder of the IC's and some other minor components. Whilst waiting on those I need to get the 2732 written with the ZX80 ROM image. The 2732 will need a small mod to work properly, but that is documented over on Grant Searles web pages.

I've also been offered a modulator by somebody on another forum, and whilst I think I'll probably fit it, I intend to use composite out for the most part. I may just replace the modulator guts with something suitable.

While I'm waiting I think I'll also get the keyboard installed, though I am flip flopping as it is quite shiny and I don't want to scratch it whilst I'm soldering some of the remaining parts in.

[rubber_jonnie]

Quick size comparison with the ZX81:

IMG20250915162546.jpg (229.52 KiB) Viewed 93 times

The changes between the ZX80 and ZX81 do make for a more compact machine, and the improved build quality of the ZX81 is a standout (At least as best I can tell based on the replica and photos I've seen of the original ZX80).

Definitely easier to see whats on the keys with the ZX81 but as membrane keyboards go, I'll take the Atari 400 over either of these