Hello Folks,
I'm trying to breathe some life into my recently acquired Nascom-1 and wonder if anyone can help please.
The previous owner told me that it was working but that after half an hour it stopped and refused to come back to life.
The original symptoms are that it displays a screen full of garbage that won't clear.
What I have so far...
I have the following voltages from the power supply :-
- 11.93V
- 4.79V
- -5.06V
- -12.06V
All look good on my scope and show very little ripple.
I have seen the clocks and the processor (Z80) is running. I can see the M1 and other signals twinkling.
I have replaced the original 2708 EPROMs with 2716s in adaptors (I can't program 2708s so I'm using the bottom half of 2716s).
I have also blown two ROMs with a tiny piece of software in each. The first fills the screen memory with 0x00. The second fills the screen memory with 0x2A ('*').
Neither seem to run until the reset button is pressed and then I get the two phots below. The results are pretty consistent but not absolutely guaranteed.
I'm sure there are clues there but I am out of my depth here.
Please can someone come up with some suggestions?
Thanks,
Andy.
P.S. This is a slightly cut down version of the story. You can read about everything I have done here.
http://www.randomorbit.co.uk/?cat=129