Sinclair ZX80 / ZX81 / Z88 Forums

Well, it's a mess but everything is connected!

Tidy up, then DRC!

mrtinb wrote: ↑Sun Nov 29, 2020 1:41 pm I was told to use MPS2369 as a replacement, and it works great in my ZX81.

Thanks I will check the footprint and get some in.

Yup the emitter and collector are the opposite way round and I think the part is obsolete too!

TR2 - the transistor used has to have a very quick switch-off time. Most general-purpose transistors take a small amount of time to turn off, especially if the base becomes saturated. If a BC548 is used the value of R6 may need to be adjusted. If the transistor used switches off too slowly, the Z80...

The ZX81 is a hard board to route (for me anyway) but I am getting there with less than 100 connections to go and I think the hardest bits are done.

Does this look right?
https://www.reichelt.com/gb/en/ceramic- ... 3.html?r=1

Making progress!

I have put that version on Github!

I deleted the mounting holes by mistake after a reimport of the circuit diagram. Luckily I did not delete the construction lines on the user layer so it only took a few seconds to put them back in.

Thanks for your help. That's what I thought but it still looks wrong to me!

Is there a known part code for the resonator? I think that will be the hardest to source new (after the ULA but we know they do not sinclair ULAs).

Yes, that datasheet for AS 6C1008 contradicts itself. It states it is compatible with "all" in one part, while only claiming CMOS levels in others. My PCB will take that chip, however. I have added the 1K, 16K switchable feature as an option I worked out how to do it. You need to add an additional I...

I think I am making some progress.

A looooong way to go.

Constructive feedback always welcome!