[sdiy] Issue with CD4024 Ripple Counter

Dave Brown davebr at modularsynthesis.com
Wed Sep 22 21:56:46 CEST 2021

In my repairs I see a lot of screwy 4000 series that died. They never quite fail but they start acting strange. I have a couple of photos on https://modularsynthesis.com/modules/tips/tips.htm


One is a CD4011 where the logic low output is 3.72V. Another was 4520 where it stopped dividing and simply output pulses the same width as the clock. I would suspect some of these are age deterioration although I have no proof. Some could be static damage which doesn’t necessarily show up immediately.


At the vintageTEK museum we get donations including parts. I’m surprised when people kept defective parts that were rejected. We get a tube of ICs that are marked reject. We got a bag of hundreds of knobs that weren’t drilled for a setscrew. Some of the rare parts I see on recent Buchla clone builds are getting worse and worse, like they were fallouts.


I like the idea of characterizing these (but I’m not volunteering). Is the date code old? I would suspect damaged or marginal parts that never got taken out of circulation.



From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Mattias Rickardsson
Sent: Wednesday, September 22, 2021 12:30 PM
To: Mike Bryant
Cc: Synth DIY
Subject: Re: [sdiy] Issue with CD4024 Ripple Counter


Mike Bryant <mbryant at futurehorizons.com> skrev:

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?


Interesting idea. But:


David G Dixon via wrote:

 clocks on both edges with switch.





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