[sdiy] Issue with CD4024 Ripple Counter
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
> 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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