I think I’m repeating myself but if it’s the first time you’ve done an APC, maybe the best would be to try the “basic” circuit (without CV without gate) on a breadboard, and if it works well try then add the rest
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Thanks.
I tried to make some fixes but even before board was a mess. Need to take a break, re-thing and solder again from the basics.
Just posted in hope, that there is some obvious mistake I did not see myself : )
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Not sure if you’ve already seen this video series - it’s a VERY thorough soldering tutorial from the 80s. It covers a lot of outdated technologies, but seeing soldering in lots of different applications really helped me understand what is supposed to happen, how to get a good joint and how to prep your work. highly recommend. I suggest watching till #8. I am also a newbie and trashed my first APC stripboard because I didn’t prep the surface and burned through the board many times because I didn’t know what I was doing. Hope it helps.
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I also started this project from the link at the start of this thread. Mainly because I thought it would be quick and easy to use with my Beatstep. When I was done it didn’t work, but I came across this thread while trying to figure out what I might have done wrong. Tried to follow all of the suggestions on here but still wasn’t working.
I even drilled out an old film tin. Analog visuals out, analog audio in haha. Couldn’t seem to find a good guide for my inexperienced noggin to use this with my Beatstep. I think I am getting a basic grasp of reading schematics though so that’s the silver lining!
I did my first successful breadboard attempt of the Forrest Mims APC that @Dud posted above and it worked great! Gonna start from scratch, skip the CV nonsense, and make an APC+Baby 8 Sequencer and put it all together in a larger film tin. Just thought I’d post my thoughts on this journey haha
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Hi all, can anyone advise how to adjust this circuit so that it could work with 12v synth supply instead of the 9v shown? Just fried one of my 555s i think naively trying to plug 12v in with the current setup. Thanks 
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An LM555 or NE555 is rated for supply voltages up to 16 V. 12 V to pin 8 with ground to pin 1 should be fine. (Keep -12 V away from it.) If that’s what you did and the 555 got fried, check for wiring errors.
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ah right. Yes, I hit it with -12v where ground should have been. Thanks for your help, I’ll order a couple more 555s and keep them away fro -12v next time
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I started over on this with a 566 chip. Used the diagram from instructables (https://www.instructables.com/Build-an-Atari-Punk-circuit-on-a-breadboard/) Everything worked fine, but for some reason the right pot causes an issue. It’s a B500k that’s wired to pin 13. When I turn the pot all the way there is a slight audio pop and then no sound all together, like it all stops working. When I switch it off and on it works again. The left pot works fine. I’ve tried a few different pots but the problems seems else where. I’ve tried building it twice and same thing happens. If anyone has any ideas I would greatly appreciate the help! I’m pretty stubborn about moving on to another project until I get this one right haha
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556, I assume (566 is an old VCO that’s no longer in production).
The APC is a very simple circuit, with an oscillator driving a one-shot pulse generator, and it doesn’t necessarily produce sounds for all possible potentiometer settings.
In many schematics (including Mims’ original), the potentiometers are connected directly between the positive rail and the DISCH(arge) pins that are shorted to ground as part of normal operations, so if you get too close to the rail you end up shorting the power supply, and may fry the chip or the potentiometer. This thread suggests adding 330 ohm resistors in series with the potentiometers, to limit the current.
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HI i´m new here on this board and wondering … do we finally have a final schematic here for a APC design that works on 12V and can use CV, and or gate for a build?
I need some help, i wanna add gate input, i dont understand where to set resistor? +9V goes to pin 4 on upper 555 which is gate pin too, i read that i need put pull resistor, what i want to know is did i need tu put resistor on +9 then wire to gate jack and after that on pin 4, or it goes +9v wire to gate jack then resistor then pin 4? And if there is no external gate input, is there need to be resistor or just when is gate plugged in, or both cases? Please help