Having checked the clocks and finding things look well, it’s time to see if the ROMs are OK.
The Nascom uses 2708 EPROMs. These are 1k by 8 bits and must have been one of the first EPROMs available. The problem with them is that they need three different voltage rails and most modern EPROM programmers can’t do that. Even my old Stag won’t. :-(.
I can program 2716s however as these only need a single 5V rail and thanks to tkc8800 I was able to make a couple of plug in adapters so I can use the bottom half of two 2716s to replace the 2708s.
I have now put Nassys3 in the two 2716s and tried that.
Still the same… Arrgghhh!