I just got a new oscilloscope. I don’t think I really need it and I don’t really know how to use it but I find them fascinating and want to learn more.
I have an old MPU 100 that I rebuilt a while back. It boots up on the bench, it boots up in a game and plays fine so I thought I’d try some tests to learn something.
I started my testing on the CPU (U9). D0 – D7 (pins 33 – 26). The wave forms looked about what I expected.
Then I looked at A0 – A14 (pins 9 – 24). Again the wave forms looked pretty expected.
Except A3 and A7 don’t show any dips like the other wave forms.
Also A4, A8, A11, A13 and A14 all show garbage.
And the voltage looks way down – 200 MV.
Why are there no dips in the A3 or A7?
Why do I get low signal on A4, A8, A11, A13 and A14?
Is there anything else I might want to look at to learn something?