Sinclair ZX80 / ZX81 / Z88 Forums

Anyone able to confirm if the readings I posted are accurate?

I guess not then. Ok, no worries. I'll figure something out.

colday wrote: ↑Mon Oct 14, 2019 8:12 pm I guess not then. Ok, no worries. I'll figure something out.

Sorry, I’m rather busy at the moment (work). I got up at 07:00 this morning for a meeting in city far from home. And have just got on the train home. I’m also rather busy for the rest of the week.

If you don’t have an answer by the weekend, I’ll try to find time to connect my oscilloscope up to a ZX81 and post up an image of the waveform and take some voltage readings with a multimeter.

The signals on these pins are high frequency DC pulses, so the actual results depends on the type of multimeter used.

Mark

Thanks Mark.

It's appreciated as I really want to get this zeddy up and running.

Quite frustrating when it's just sitting there and I have no idea what to do next.

Is there a document anywhere with specs for the ULA and PIN outputs etc?

I'm thinking I may create one if not as would be useful for reference.

I was given this page from a forum member:

https://www.worldofspectrum.org/hardware/rep3.html

Martin.

A quick scan read and that looks good. I shall have a bit more of an in depth read. Thanks muchly!

Edit: So having read it, it looks like I need a logic probe...

More expense.

Can I grab a cheap one from China? Or should I look at buying a branded one?

I bought the cheapest from China.

mrtinb wrote: ↑Wed Oct 16, 2019 9:49 pm I bought the cheapest from China.

A post with a useful collection of pin outs (including Z80, ULA, ROM, RAM) for ZX81s is linked to in my sig. below...

Mark