Re: I found it! A very sorry looking MK14.
I've got dozens of vintage TTL chips, but not a single 7445 among them !.
Although I'm now fairly certain the problems lie in the ROMs or RAMs, I have one last check on the PCB.
I don't know the orignator of this VI board, but there is a number on the back which I think is a fab shop batch identifier.
The number is in tiny print, an inch below the 'S' of science. The number on my board is '2364469A-Y118-200602'. If this matches any known working VI them we know they came from the same production run, and mine should be OK.
A faulty PCB is a real long shot. All the points I've probed with a scope show good signal levels and shapes, and I even dug out my 308 logic analyser ( contemporary 1981 kit !) to see the what the data bus looked like for reads and writes. ( I must learn to use this bit of kit properly, I've had it long enough. )
If I don't get Vicky working, I won't get Micky working either.
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