Thanks @CTorp, that’s good to know.
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I finally got to finish the first VCO build.
However I just connected it for the first time and the thing is behaving weird.
If i just connect the ramp-out, there is no sound at all, but as I touch the wire on the center-pin of the 12-pole selector, there is sound…
I did not get the exatc 12-pole switch that’s recommended on the BOM, because I couldn’t find it for sale in Germany.
I got this one instead:
And here is a video of the behaviour:
Does anyone have an idea what’s wrong?
Cheers
You’re one big antenna, so that things change when you touch random wires isn’t that surprising. But maybe not that much. Could be some floating connections somewhere, maybe (i.e. bad solder joints on pullups or pulldowns).
Have you done any basic calibration/sanity checks? (the 4 V trimmer, octave switch voltages, etc)?
I had this exact problem on mine. There was 2 issues. The tab inside the pole switch had shifted out of the correct slot,so when I got to one end of the octave select it would make that sound. As far as touching the wires, even though I was meticulous with the molex connections, the problem went away when i removed them and soldered directly. Also it really sucks when the 12 pole switch comes apart when you are putting the knob on, and the microscopic ball bearings pop out. 2 of mine did this.
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It sounds like it is working its just very very low. I recon its a cold joint somewhere. if you have a soldering iron with a temperature gauge, heat it up more and reflow everything, especially solder joints that look like they are attached to the ground plane, as they take longer to heat up because your in effect heating up more metal because of the ground plane. but I think it is definitely fixable! just a case of finding that 1 annoying little thing
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ok, i tried reflowing all solder joints i thought didn’t look so good. i removed the molex connector and wired directly to the pcb. now my body isn’t working as a pitch knob anymore, but the sound is still very low, only clicking noise. the tune-knob and pwm seem to work (clicks change speed as i move them), however, the octave switch doesn’t do anything it seems. i calibrated the 4v think btw, not sure if the other 3 trim-pots do anything atm…
here is my 12-way:
If you’re hearing clicking sounds and they change speed, it’s probably just tuned below audio range. Give the trim pots a good twiddle and you should start to see results.
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Have you checked the voltages on the octave switch (they split the 4 V reference in four parts, so should measure 0, 1, 2, 3, 4 V). For the other pots, this might help:
tried that. cntr changes clicking speed a little, the other 2 don’t seem to do anything.
yes:
pin5 - 0V
pin4 - 1V
pin3 - 2V
pin2 - 3V
pin1 - 4V
(measured from 4V ref. point)
btw - what does the middle wire on the switch actually do?
It brings back the selected voltage, so as you turn the switch you should measure 0V, 1V, 2V, 3V, and 4V on the middle wire.
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glad I am not the only one. one of my switches is still missing one ball , never did find it …
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ya, works but the action is not the same. probably end up ordering a few more replacements
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okay, any idea what could be wrong with my 12-pole-switch above? the adjustment-pots and tune knob at least change the speed of the clicks in a way, but the 12-pole doesn’t do anything… also when i touch the pcb around the soldering pad of the middle wire from the switch with a cable, i get those pitch-sweeps and noise again,…
i just noticed, i use a L7805ABV instead of the L7805CV that’s linked in the BOM. Is there a difference? Could this have something to do with my problem?
Per Mouser, the differences are the L7805ABV provides higher output current, higher PSRR/ripple rejection, and lower line regulation, and can operate down to 40°C. In other words, it can only do a better job.
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(not sure the amp difference is correct (datasheet says “up to 1.5A” for both, and they have the same °C/W and max specs), but the A version does indeed have better voltage tolerance and regulation, and is available for wider temperature ranges. Not that any of these specs matter here, though 
– you’re regulating regulated 12 V, and if the Arduino needs more than 1 A or you find yourself jamming in −40 °C 
you may have bigger problems.)
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ok, so when i removed the molex connector to wire directly, seems i damaged a track on the pcb. see pic below.
if i read the schematic correctly, the middle pin of the 12-way-switch basically goes directly to pin3 of the TL074, is that correct? do you think i could try wiring it directly?
cheers
Yes. But Discourse will not allow me to simply say so without dumping a load of other garbage into my reply.
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yessss!!! finally it works!!! thanks for all of your help! going to calibrate the thing now! cheers!
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