Eh she’s working good now. Didn’t change anything lol.
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Well might have been a loose wire then. Does everything stay working if you touch the wires (e.g. tick against them with a pencil)?
@Jos There is a 1918 US Signal Corps crystal radio, as well as some other vintage test equipment,etc, and a very messy work station.
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And those drills must have been used to make holes for mounting radio tubes I guess 
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Refloat, retest, repeat. A standard part of many a build. 
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You didn’t get one of the old 3.3v Nano variants by any chance, did you? I don’t know if that would explain why it worked when you touched ground (taking ground “lower” or changing the capacitance or some such thing) but it would certainly explain a lot of misbehaviors.
Getting it to misbehave again…hmmm not sure what else to try
Re-seat the nano and test it is doing what it should on a breadboard without all the hardware. After that it would be continuity and solder joint testing plus making sure all grounds lead to the ground on the nano.
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Ok got it fixed. Added 10k pull downs between the two switches and their inputs to the arduino. No theramin issues anymore! Yay
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Really appreciate all you guys for your help!
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Weird because if things are connected like 8-Step Arduino Sequencer then there already were resistors there, electrically but not physically the same place. But if it works it works.
[Edit] Oh wait, the zero switch position’s resistor is new since there isn’t a zero jack. Maybe that’s it?
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Oh I see what you’re saying, let me try with just the one in
What, and mess with a working circuit!?
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Nope. Don’t think so. Measured the voltage coming out of the gates of the arduino… And measured 4v. Also supply from the arduino’s 5v is 4v… Voltage coming in is 5v from the 78l05… Weird… Looking further on the interwebs in the direction of arduino’s giving 4v.
Hmm, I think I read the recommendation is to power a Nano off 7-12V on the VIN pin. I think it’s OK to power it on the 5V pin from an external regulator. But the onboard regulator needs more than 5V in to get 5V out.
But don’t take my word for it.
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Just quickly looked it up… You’re right… I’ll try it out. That means his stripboard schematic isn’t correct. Doh! Well… With every mistake you learn something…
Is the external regulator really needed, I wonder?
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Yup that’s what I did… Just going to try it without the regulator and see what happens…
Yeah, don’t feed 5V to VIN if you want 5V out, the onboard regulator will shave off ~1.2 V and while the AVR can run at lower voltages it’s only speced at 10 MHz for <4.5 V (see here and here for a bit more on this). It probably works well enough in practice that you might not notice unless you really need 5 V out and pull out your scope/multimeter, though 
If you should use an external regulator or not depends on your VIN and how much milliamperage you pull from the IO pins; the onboard regulator doesn’t have that much spare capacity, and is harder to replace than a separate one.
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