[sdiy] Issue with CD4024 Ripple Counter

Magnus Danielson magnus at rubidium.se
Tue Sep 21 11:09:36 CEST 2021

Where is the 100 nF decoupling capactiros over the power-lines of each chip?


On 2021-09-21 03:18, David G Dixon via Synth-diy wrote:
> Just for Ss and Gs, I thought I'd show you my layout graphic for the 
> ASR board which has the clock circuit on it.  Please see attached.  
> Note that red traces are the +V rail and green traces are the GND rail 
> (and black traces are the -V rail).  The CLOCK pin of the 4024 is 
> connected to the light blue trace.  I've also attached what I call the 
> "Build" picture, which is what the board actually looks like.  
> Finally, I've attached a picture of the actual board.  Note that there 
> is another circuit board that this one plugs into, which has a DG333 
> and comparators for controlling the "Shift/Bypass" switches on each 
> ASR channel electronically.  That's what the 3- and 4- pin headers 
> plug into.  The 4-pin header passes through that board and connects to 
> the Panel PCB.  This is where the clock signal comes in and out of 
> this board.
> The rail traces are a bit thicker than the other traces.  You will 
> notice that the ground traces do not connect to each other across the 
> top of the board, so that the ground at the 4024 actually comes up 
> from the bottom.  I just tried jumpering the two ground traces 
> temporarily with alligator clips and it had no effect (and why should 
> it?).
> Also, I should mention that when the ASR is being clocked by an 
> external LFO, the CD4024BE is clocking on the positive edge only.  
> However, when the Manual clocking switch is used, the CD4024BE is 
> clocking on both edges.  The clock signal at the CLOCK pin looks 
> identical in either case.  The manual clocking switch is connected to 
> the +V and GND rails, and is fed to the comparator through a 1k 
> resistor, whereas the clock input jack is connected through a 10k 
> resistor.  Why any of this should have an effect is beyond me.  This, 
> for me, is now more or less in the realm of the supernatural, in terms 
> of my ability to understand it.
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