Sinclair ZX80 / ZX81 / Z88 Forums

Hey guys,

I have a ZX Spectrum recapped, composite modded, TR4, TR5 and Diodes replaced and I'm getting this picture with no Lower RAM installed.

Anyone ever had this kind of issue?

Thanks

Hello and welcome to our forum.

It is hard to tell from your photo, is there a border around the central coloured area?

This video shows what should happen for a normally working machine.

With no lower RAM, the CPU should still be able to execute the start of the ROM code after power up or reset, and one of the first things it does is to set the border to white.

At a guess, I would say that the ULA could well be faulty.

But first, do you have a multimeter, if yes, what voltages do you get on the +5V, the +12V, the -5V (all on either the edge-connector or the pins of the 4116 (or equivalent) ‘lower’ DRAM chips (see the link to pin-outs in my sig below). And what voltage do you have on the (nominal) +9V input?

Also which issue board is it?

Mark

Good morning Mark, I guess it's an issue 6A (from the subject)

Gahhh!!! Can’t see the wood for the trees Thanks Paul

So being an issue 6A, at least it has the latest version of the DC/DC converter circuitry.

Mark