No I don't have a schematic, but it is a small PCB. The _WR line also
goes to 2 DRAM chips, but nowhere else as far as I can tell.

Yes, the CPU could be faulty, the RAM could be faulty, the EPROM could be
faulty, and a few other things too.
This is a very old board.
(Apart from the EPROM, and now the chip I replaced, none of these chips
are socketed)

I will go back tomorrow and see if I can see anything else on the scope
that might look a little suspect, and what, if anything, is actually
happening - I didn't get much further than noticing the _WR was definitely
screwy.

Cheers,



Gareth.


Not supposed to be a pull-up on that /WR line maybe ? Little sm resistor
gone open ? Worth hanging a 1k up to rail in case some internal pull-up on
one of the chips has gone open ?

Arfa