Leaderboard

Well, what a start to the morning. Connected the input port to ground, as I did yesterday, and of course nothing. Then I remembered it's got to be to the -12v, not ground. So what happened next. What can I say, all the CPU boards that I'd fixed blind all worked as did both the I/O boards. One point of note is the 12K board did actually get the 2.4KHz interrupt out to the CPU even without the link whereas the 8K's did nothing so that's solved that conundrum. Next step is to get some sort of test rig together to check all the I/P's and O/P's. That's the easy bit. Thanks to all for getting me off the bottom rung and Wizard with that snippet of code. So obvious when you know.

The board I use for RAM adaptors is double sided through hole matrix but with no tracks. It comes in various sizes and I cut what size I need. You can find them cheap on Ebay. For example:- https://www.ebay.co.uk/itm/Drilled-Double-sided-Copper-Prototype-PCB-Matrix-Epoxy-Glass-Fibre-Board-70x90mm/232524667208?hash=item36238cd948:g:CZcAAOSwu4BV6Xge:rk:30:pf:0

No more ROMs for Alex please - he needs to go for a lie down in a dark room for a while!