[sdiy] Issue with CD4024 Ripple Counter

[David G Dixon]

Hey SDIY Team,

Here is the latest (and probably last, from me, at least) on the 4024
saga...

First of all, the ASR module:

1) I changed the 2.2nF cap in the switch debouncing circuit to 100nF.  That
switch ain't bouncing!
2) I changed the 100pF cap at the 4024 CLOCK pin to 2.2nF.  Now the negative
edges are reverse-J-shaped on the scope.  There are no glitches whatsoever.

Result: No change -- MC14024BCP and CD4024BCN still work perfectly, CD4024BE
still clocks on wrong edge with signal, and clocks on both edges with
switch.

Next, I built Tom Stinchcombe's test circuit on a breadboard and tested
that.  The circuit diagram I drew in MultiSim is attached, as is my
breadboard layout (yes, I lay out all my breadboards), and a picture of the
breadboard.  As you can see, the circuit is very clean, and my breadboard fu
is very strong.  Also note the careful power-rail decoupling (which I can
confirm had absolutely no effect, because I forgot to install the caps the
first time).

Result: CD4024BCN clocked on the negative edges (correctly), and CD4024BE
clocked on the positive edges (incorrectly).

Conclusion:

These CD4024BE chips are defective.

Alternative conclusion:

If they are not defective, then they simply cannot be clocked correctly by
David G Dixon, so they are useless to David G Dixon.  YMMV (but I'd guess
not, because I am not actually doing anything wrong).
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