Is this possibly a bypass cap issue letting glitches get out on the power bus?
(I tried to build a digital (TTL) doorbell back when before I understood the
finer points of layout and bypassing - it worked as a prototype but when I
hooked it to the actual doorbell button wiring it started going off,
sometimes in mid sequence, every time a light switch was flipped etc....)
73, Al
On Thu September 22 2016 8:54:34 pm Louis Ciotti wrote:
> Small update...
>
> The new CPU arrived, and that did not fix the problem.
>
> I spend a few minuted scoping lines again, and I started to to single
> sweeps with the scope, and I noticed something odd on some of the lines.
> It appeard to have some random spikes or dips in the logic levels. I need
> to verify this when I have more time, maybe next week, but I am wondering
> if there might be some contention on a bus... I need to really look at the
> address lines now, I wonder if there is a bad IC on one of the address is
> lines....
>
> On Sat, Sep 10, 2016 at 4:34 PM, Louis Ciotti <lciotti1@gmail.com> wrote:
> > OK so I thought I was making good progress resurrecting a paragon, but
> > now I thing it may be "brain dead" . It worked the last time I had it on
> > the bench, but now when that I have time to finish getting it back
> > together, when I turn it on all I get is random LEDs lit up, nothing and
> > nothing on the display, and no audio output. The last time it was on the
> > bench everything worked, just needed to fix the headphone jack...
> >
> > Did the processor or memory die? Any thoughts on debugging this?
>
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