Re: strange 2001N fault

Can anyone with a working 2001N and a suitable two channel scope (or
logic analyzer) please send me a picture of these two signals
together?

Channel 1 (triggering on H-L transition): /RAS (pin 4 of any 4116),
ideally you should have a slow enough sweep time to get at least two
/RAS pulses on the same sweep, since one will be a refresh pulse (it's
on low phi2, if you want to check) and one will  be a RAM access (on
high phi2)
Channel 2: MUXA, found on any pin 14 of UE3-UE6. MUXA should remain
low on the refresh /RAS pulses, and should toggle somewhere after a
RAM access /RAS pulse.

I believe I have a bad MUXA on my 3032, but I have currently no other
board to check (but a few 2001, that has static RAMs, so very
different in this area).
Thanks in advance.


On Tue, Feb 20, 2018 at 11:53 AM, Francesco Messineo
<francesco.messineo@gmail.com> wrote:
> Hi all,
> in case someone doesn't read vcfed forums, my 3032 developed a strange fault:
>
> http://www.vcfed.org/forum/showthread.php?62202-3032-(2001N)-strange-fault
>
> The thread link is just to recap what I've found and what I did, so I
> don't have to type all again here ;-)
> Ideas welcome, I'm just scratching my head. This is probably where a
> logic analyzer is needed badly.
> It seems to me there're unintended writes on some ram locations (not
> so random, address wise) and it makes me think about VSP crashes on
> C64.
> Any idea where to look for a fault?
> Frank

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