I played around with some basic chip re writing a few months ago, but now I can't get it to work. Help would be appreciated.
When I read a chip the buffer shows all 90h's and a memory check shows 'not empty'. I've tried different eproms, different computers. I even bought a new Programmer (basic Chinese Willem programmer), with new cables and everything. The chips are 27C256's and I set the dips up accordingly. I've left them on the eraser for varying times, but even a brand new chip shows the same thing.
The instructions are pretty basic, but I assume the eprom goes in the lowest position on the ZIF socket closest to the dip switchs and pin 1 of the eprom at top left.
It worked before, what am I doing wrong.