Sinclair ZX80 / ZX81 / Z88 Forums

I love Lardo’s idea. Me too. That's exactly what I'd do if I had room for one. It looks like I'll just have to settle for composite to HDMI. That's not necessarily terrible though. I was watching this video last night to see just how good it's possible to get the composite video looking if you're h...

...and costs twice as much ready built as I paid for the +2.

And that's the crux of the problem. I'd love to use RGB, but I'm in the same boat as millions of others with no choice but to use either a UHF TV signal, DVI or HDMI as none of my displays support anything else. I've looked at several converters on eBay and Amazon for around £30 that clearly state "...

Using the digital display data, they can then process it however they like and hence can output new sharp video streams. This is a much better method than sampling the original output from the ULA, or worse, the composite video signal. From a purely technical perspective, this is clearly the best w...

This one? I guess probably not as you're asking about a case rather than an entire Speccy clone.

I think this looks great, but £300 for the base model?

https://www.kickstarter.com/projects/sp ... xt-issue-2

Have you cleaned the edge connector on the ZX Spectrum?

If you don't have a fibre-bristle pen, an ink eraser works fine as long as the abrasive in it isn't too coarse. The blue end of a Faber-Castell eraser works fairly well if you're gentle with it.

A long shot I know... If you used the modulator can as the ground connection for the composite video mod, try giving the can a wiggle. I only mention this as 2 of the 3 ZX81s I've played with had dry joints on both of the modulator can legs that solder through the PCB. This could lead to an intermit...

I finally got around to having a proper look at this one. It was just the dodgy 7805 regulator that needed replacing, so it now has a switch-mode jobby. I've already slapped a big heatsink on the ULA and given it a Zigg's composite video mod inside the gutted UM1082 modulator can. Next up will be a ...

Yes. 100nF is far too high. As Mark said, what you're trying to do is shift the RAM timing to within a window where it behaves as expected by the rest of the hardware. If no value between, say, 33pF and 470pF fixes the problem then going higher will likely achieve nothing except placing unnecessary ...

ILAH wrote: ↑Sat Jun 17, 2023 11:49 am I tried some caps. Up to 100 nF i get the first result, 200 / 300 nF make second pic. Higher nFs keep the ZX81 freezing with black screen or artefacts.

That's way too high. Please be careful as there's only a 680R resistor between your capacitor to ground and the /RAMCS pin on the ULA.