built them at the same time with the same components, so there is nothing obvious to blame
or at least not obvious to me, wondering if you guys mind walking me through some troubleshooting, becasue i dont even know where to start
the little green light on the arduino comes on, but that is it, no lights or anything on the front panel, nothing from any output
what do you reckon?
First, the Arduino bits and the VCO are almost entirely separate, so you may want to focus on one of them at a time – I’d start with the VCO.
I assume you have a multimeter? First thing to do is to measure the DC voltages at the 3340 supply pins, and the CV voltages on the various 100k resistors that lead to pin 15, relative to ground.
I should do a drawing for the #1222 PCB, but in the meantime this annotated stripboard might help you locate some measurement points:
When powered on, pin 3 should be −7.2 V or thereabout, pin 12 should be 0 V (GND), and pin 16 should be +12 V.
Pin 15 is the CV input, which is 0 V too if you measure it, held there by the internal summing amplifier, but you can measure the total CV by measuring on the other side of the 100k resistors that lead into that pin, and summing up the values (at A or B in that picture, but these are elsewhere on the #1222 PCB). You want at least a few volts there in total to get an audible signal (see here for more).
The values to the left are resistance values, and should be measured with the power turned off. You can measure directly between the 3340 pins on the #1222, i.e. pin 1 to 3 should be roughly 30k, pin 2 to 3 should be 5.6k.
EDIT: Spelled out the expected voltages here as well.
Start by checking power. Presumably you have no shorts between ±12V and ground or your power supply probably would’ve tripped off or something, but check you have +12V or -12V or 0V on all your ICs’ power pins.
i understand the concept of this but no idea how to put it into practise
checking DC? the symbol with a solid line and a dotted line underneath
putting the black (COM) peg on ground, not sure what ground it, putting it on one of the pot holding clips
putting the red (INPUT) on the one im trying to test, tried each one and getting no reading at all, but there are little crackles and sparks if i go too near another pad.
got my multimeter set to 00.00 V in terms of reading, should totally be seeing something and im not sure what im doing wrong
this is quite far above my head, i dont even know how to use my multimeter yet!
how do you know which pin is which (numerically) on the 3340
“lower left” when the IC is oriented as shown: usually there’s a notch or semicircular depression at one end, pin 1 is at that end. (Sometimes there’s instead a circular mark near that end, but sometimes there’s both, one at each end — in that case go by the notch. Also, printing on the surface of the chip will be right side up when oriented correctly.)
It’s not hard, just a *lot* of things to learn at once 
@Caustic made a video on using multimeters here, which might be useful:
To find pin 1 on an IC, look for a dot near the pin, or the side with a notch (some have both). The pins are then numbered counter clockwise:
The text is also a strong hint – if you hold the circuit so you can read the text, pin 1 will be in the lower left corner.
(There’s sometimes a circle on the opposite side, but ignore that if you see any of the others. Post a photo if you’re not sure.)
EDIT: Added some label text things to the pinout.
Borrowed an AS3340 photo from Electric Druid and scribbled on it:
tl;dr To check continuity, DISCONNECT POWER TO THE MODULE. Look in the manual for your multimeter to find out how to get into continuity mode, touch probes to the two points you want to check continuity between. If it beeps, they’re connected.
To check resistance, do the same with the voltmeter in resistance mode and read the value.
To check voltage, connect power to the module. Put the multimeter in DC voltage mode. Carefully touch the black probe to anywhere that’s supposed to be ground, like the strip marked as such in the diagram linked above, and the red probe to the point where you’re checking.
ah nice, ok first things first
i just cant work out how to do any of the multi meter readings
Here is a video of my confusion
ok ok ok scratch that
where im putting my ground is apparently very important, taking a ground from one of the middle pins on the IC im getting accurate -12V and +12V readings
so onto the 3340, i took readings at the pins noted and got
3= -1.6V
12= 0V
16= -1V
presuming im meant to be taking ground from the IC pins to get an accurate reading?
This video was me a few months ago. Make sure you are putting the ground (black lead) on pin 12. That should be hooked up to ground (from your power supply). Take the other (red) lead an put on 3 and 16.
If you get those same values you mentioned, we should check the power supply itself next i think.
Here is the pin info for the AS3340 for reference:
ok cool, yeah im still getting my head around what ground is
did as you specified and still got the same readings, at least its consistent!
in terms of psu im using a tiptop uzeus, i didnt really question power becasue i have built 2 and one works
seems like power isnt getting from the IC to the CEM?
Disconnecting power and doing continuity checking is easier, for one thing less worry about shorting something in the process. Check continuity from the 680R resistor that’s connected to pin 3 to -12V on the power header, from pin 12 to GND, from pin 16 to +12V. If all three beep (and if there’s no shorts between ±12V and GND) then power to that chip should be good, aside from the possibility of a bad connection between the 680R resistor and pin 3.
Likewise check the TL072 pin 4 to -12V, pin 8 to +12V. There’s no ground connection on that chip.
Edit: Sorry, for some reason I was thinking you were building the stripboard version, but same idea applies. 3340 pins 12 and 14 and TL072 pins 4 and 8 should connect directly to power, 3340 pin 3 through the 680R resistor. Check TL072 power pins, if they’re OK it’ll narrow down where the problem is. Also there’s a TL074, pin 4 should connect to +12V and pin 11 to -12V.
right i forget that the subject of this thread mentioned one worked. What we need to do is find where the power starts to get a bit wonky. I dont have this circuit board, but there should be a place where it get power from like a 10 pin ribbon cable. i would use that for your ground reference to start. By reference i just mean you poke the lead of the multimeter there, and thats where it gets “ok this is ground” from.
Oh, yeah. start with continuity testing. as @analogoutput suggests. If you want to know how to do that, its in that video @fredrik posted earlier!
Also, dont be discouraged. Theres a lot of jargon to learn so dont hesitate to ask if we say something and you are like: “the fucks continuity testing?”.
guys firstly thank you so much for the help, this is pretty fun now i know how to use my multimeter
SO TL072 pin 4 to -12V is fine but pin 8 to +12V got no beep
3340 pin 3 itself isnt connected but the other side of the 680R resistor goes to -12V fine (im assuming you cant check continuity through a resistor until there is power?)
pin 12 to ground all good
pin 16 to +12V no beep
So sounds like a +12V problem. Is there continuity from pin 4 on the TL074 to +12V?
“Continuity” means no resistance (for certain values of “no”), so if there’s a resistor between the two points, no beep. So what you observed was correct in so far as pin 3 goes. And you don’t check continuity or resistance with power on.
Edit to add: It’s interesting you say the LED on the Arduino lights up. That’s not with a USB cable plugged in, is it? (USB should not be plugged in and power applied on the main board at the same time.) If it lights up without the USB plugged in then +12V is getting to the regulator. In that case you do have +12V on the board but it’s failing to get to both the 3340 and the TL072. There aren’t many ways that can happen. (One way is bad solder joints on the +12V pins on both ICs.)
Will have to check on the TL074
Yeah the nano is getting power with no USB, so yeah it’s coming from the board
Maybe I should try changing the IC, giving it al clean up
The USB power line is connected to the Nano’s +5V rail via a diode (described as “auto selector” in the schematics) so as long as your USB supply is 5 V and you don’t have weird ground loops, the Nano can handle that. But if you want to play it safe, only use one at a time.
no continuity between pin 4 and the +12V
so yeah its definately a problem with my +12V just not making it anywhere on the board
I changed the IC connecter, a bit of a hack job and had to surface mount another one, but its still the same, continuity from ground and -12V to everywhere it should but no +12
what do we reckon? i looked at the schematic and it doesnt really seem there is much that can go wrong between the +12V and the pins that im checking continuity on
