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When I first saw it I thought it was a biscuit (cracker). Good work on using what you have got.
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I think Iāve had the mosfet in backward, but my 1222 has been working well, I think, just realised when building a second one. What happens if itās in backwards??
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Ah looking at the video itās to protect the arduino
Most fets (mosfets and jfets) can be operated symmetrically, that is, you can swap the source and drain and it wonāt be a big deal. Some devices are optimised for a specific orientation, but even then theyāll still work when in backwards. As long as the gate is connected correctly everything should still work somewhat normally.
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Oh wow, thanks! I guess Iāll just leave the working one alone
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Is that U5 though? I just had a look at the schematic and if it is itās not a mosfet but an L7805 voltage regulator - and that probably wonāt work properly when itās around the wrong way.
EDIT: It looks like the arduino nano vin pin is connected to its own voltage regulator and can handle between 6-20V, but yeah, check the voltage at the vin pinā¦
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Yeah it is U5, the video says most ārealā arduino save their own voltage protection but others might not
Yes, but the arduino is driving a 7segment display, which needs quite some current.
Better drop it on a 7805 with a big metal tab, than on an tiny SMD one.
And you desolder the 7805, replace it with a 7808, because it is connected to Vin, not the 5V pin, which means the onboard regulator is in series with the 780x, and to works outside its specs when powered thru a 7805, but OK thru a 7808.
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I finally got all of my VCOs calibrated with the help of the wonderful guide provided, but I ran into a sort of small problem. When I plug my midi to cv converter into the 1/V input of the VCOs, they go way out of tune, with each octave on the octave switch outputting a random note at a random octave and everything being out of tune. I would even play middle C on the keyboard and bring the center note down to C3 and from there itās all out of tune again. Like I mentioned, I already calibrated the oscillators by using the guide with the octave switch on the VCOs which worked fine for me when getting the 4.000 frequency ratio. However, I have no idea if I have to calibrate them using the alternating 0V and 2V on a keyboard method if I plan to use a midi keyboard or what the work around is when I already calibrated them with the first method then wanting to use a keyboard on them. If I have to recalibrate them, would I have to still aim for the 4.000 frequency ratio with the alternating 0V-2V on a keyboard method? If so, would I need to calibrate them with the octave switch on the lowest position or does the position of the switch not matter? Or is there a work around this? Iām really curious because I am in love with these types of oscillators but I always bump into something I only overcomplicate more
Howdy, Iāve just finished assembling my second 1222 and unfortunately itās not going as smoothly as my first one.
The LED display is jumping all over the place and Iām only getting the slightest, barely audible output.
The reference voltage is set correctly, Iāve refloated all of the solder points, Iāve replaced all of the ICs and the Arduino, Iāve checked to make sure none of the pins under the sockets are bridging, Iāve made sure all of the component values are correct and can confirm that the rotary switch is wired correctly.
Before I spend the next few hours hunting down the culprit with a multimeter I thought Iād ask you lovely people if you can maybe think of an obvious mistake I might have made? Any help would be much appreciated 
Cheers!
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I would check this (@Dud style 
)
And your 2k resistors at the top, maybe it is the photo but they seem to have a different color coding.
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Is the 7seg displaying the correct letters? is the polarity in the code corret?
Rob
I dont see any 2k resistors on the rotary switch . what is the green and yelow stried device on pcb?
Thanks mate, Iāve resoldered the points your highlighted but unfortunately no change.
The resistors in the top left are definitely 2K, one just has a stripe worn off.
@twinturbo Slowing down the recording I can see that the display is showing the correct letters, itās cycling through them but not in any particular order. Could you tell me how I might check the code polarity?
Cheers!
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Itās at the top of the code, but if your seeing the correct letters itās not the problem.
but remember the display is just that, itās not like the arduino is providing any feedback into th etuning. So if thereās garbage in then itās going to be random.
Apologies for the delay. I put electrical tape over the data port to avoid plugging power in there
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Iām having trouble tuning the vco/ octave selecter switch thingy. I bought a tuner, but i cant really make sense of it. My lack of formal music knowledge comes back to bite me i suppose. I think i could do a better job if i can use the 1v/octave principle to tune this thing, but what points to probe to do this? In other words, where do i stick my probes on the 3340 or the pcb to get this voltage to help me tune the octave selector?
I know i could probably find out on my own but please excuse me for using you more knowledgable folks as a shortcut, because im afraid not getting this tuning stuff done will discourage me from this whole synth project wich would be such a shame.
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About all you can do with the multimeter is to get an accurate 4.000 V at the test point.
Beyond that, unless you have a very good ear and a relaxed attitude toward being in tune, you really do need some way of measuring the frequency (pitch). If you have a tuner or frequency counter or oscilloscope that can display frequency in hertz thatās easiest. An octave means twice the frequency, so you adjust until a 1-step change on the octave switch results in a doubling of the frequency, like from 500 Hz to 1000 Hz.
If all you have is a tuner that displays how close you are to a note like C or D or F# then you need to adjust until a 1-step change takes you from some note to the āsameā note but an octave higher, and if your ear canāt tell if itās one octave or two or what there may be some challenge. Maybe a musically trained friend could help.
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I played around with the tuning for a bit but gave up. Like you I have no formal (or informal) music training. Donāt let this discourage you though. I still make some really good noises with my modular. I (you) know what sounds I (you) like. Mess around with the filters and other modules. Mutable Instruments Clouds is a key module in my setup. Push crazy beeps and bops into it spin some knobs and see what happens.
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