Sinclair ZX80 / ZX81 / Z88 Forums

If you prefer tactile feedback from a keyboard try one of these:

https://www.ginger-electronic.com/en/re ... model-zx81


At the bottom of the page is a regulator replacement that works in the zeddy:

https://www.retroleum.co.uk/spectrum-repairs-mods

Note that Retroleum cannot post outside the UK at the moment thanks to some cyber criminals hacking the Royal Mail.

Thanks for that Lardo Boffin.
Looks like a useful page for the components although I will probably source the regulator and other components from here in New Zealand as much as possible. They seem to be very cheap which is a bonus. I havent posted anything here for a couple of weeks because im wainting on parts to arrive from overseas. (an official power supply and quite a few other things from the UK.) Everything else I can probably find here.
I really like the idea of upgrading to a slightly better keyboard. Ill see how the membrane ones go before I decide. I recall seeing old magazine ads where you bought a completely new housing with a propler commodore 64 style keyboard. I wonder what happened to those? Not sure id like that though because it wouldnt look like a ZX81 anymore.
When I was a kid I remember buying this stick-on keyboard with better buttons that you put over top of the membrane keyboard. From memory it worked surprisingly well for a cheap accessory. Not anywhere near as good as a mechanical keyboard or even a spectrum keyboard. But still much better. A quick google search and I even found this pic of it.

So here's where I'm at with this project. Finally everything I need to get started has arrived. (well everything that had to come from overseas).
Also as a bonus a second boxed ZX81 that I bought from someone in the UK on ebay arrived and its in perfect working condition. Honestly the RF image was so surprisingly good that I'm leaving it stock and unmodded.
Ill be doing all the modding on this USA model. So yeah. I give it power and there's nothing, so i'm pushing ahead with the replacement of the 7805 regulator and the 22UF Electrolytic Capacitor that 1024MAK kindly suggested (because of the damage i probably did when i used a power supply with the wrong polarity). Both parts are cheap and readily available here in NZ.

I do have a question about one part though. A local retailer was selling this 22UF capacitor but its 50v instead of 16 or 25.....
https://www.jaycar.co.nz/22uf-50vdc-low ... r/p/RL6430

This is to replace the 22UF that is in the C3 position on the mother board. Is this appropriate?
There was this other Tantalum 16v 22uf capacitor but the lower voltage and the fact that it looks very different from the existing component kind of put me off...
https://www.jaycar.co.nz/22uf-16vdc-tan ... 446289bec3

Also here is the 7805 regulator im buying from the same retailer....
https://www.jaycar.co.nz/7805-5v-1a-vol ... e/p/ZV1505

Thanks heaps.....Glenn.

gl3nnium wrote: ↑Sat Feb 18, 2023 10:24 am I do have a question about one part though. A local retailer was selling this 22UF capacitor but its 50v instead of 16 or 25.....
https://www.jaycar.co.nz/22uf-50vdc-low ... r/p/RL6430

This is to replace the 22UF that is in the C3 position on the mother board. Is this appropriate?

Yes, that one is fine. It would be helpful if Jaycar were consistent with their facts though. The title says 50V, but the text says 25V!
In a ZX81, a 25V or greater voltage rating is fine. As long as it’s not too silly a rating such as 400V…

The 7805 that you linked to is also okay.

Mark

Thank-you kind Sir!
As always your advice is hugely appreciated. Will get both parts and commence surgery within the next couple of days. Will post here with an update on how the patient is doing.