[sdiy] Issue with CD4024 Ripple Counter

Mike Bryant mbryant at futurehorizons.com
Wed Sep 22 17:09:45 CEST 2021


I wonder if the CD4024 has an inverter on the input and both the faulty ones have blown the inverter by static, hence the signal just punches through unchanged and clocks on the wrong edge?

On 22 Sep 2021 11:19, David G Dixon via Synth-diy <synth-diy at synth-diy.org> wrote:
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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