Pin 15 is a summing node that’s held at 0 V by the input buffer. You should measure the voltages on the other side of the 100k mixing resistors (R19, R22, R23, R24, R25).
See here for approx voltage to frequency:
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Thank you, that’s what I thought because I re-read your earlier statement.
So if I measure >9V on R23 I should get an audible signal from using a Audio probe on the pins 4, 6 or 10 and that would mean the chip is broken as I can’t get anything out except a constant hum when I turn my volume up - no matter what I do with RV6 (I turned it slowly from one end to the other), right?
My next step would be to order new ones and try this then… 
Hey Guys! Finally got round to building my first 1222 oscillator, and I’ve run into some trouble. With the rotary switch, I’ve wired the pins to the labelled pads on the pcb, but I don’t know where to connect ground. It’s probably a pretty noob question but I’m stuck! Any help appreciated, cheers! 
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Watch from here:
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I did try and follow that, but he’s using a molex connector, whereas I’m just using wires. I couldn’t follow where the ground wire went 
Is that the centre pin or the first labelled pin? Sorry I’m just confused 
ground goes to pin 1 on rotary switch and the hole [ where molex would be ] opposite the ground with the arrow pointing to it goes to the center pin on rotary switch
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Cheers for the help guys! I’ve sorted it now
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glad you got it sorted!!! just saw yeah I mainly put the writing gnd and the arrow incase someone had a mod in mind!!! glad its sorted looks neat!!!
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Okay so I’ve officially given up with this build. Would someone be willing to let me send this thing to fix it? I’d be happy to pay you like a pcb or something for your time.
EDIT: Someone already contacted me and offered to help 
Hi there!
Today I plugged the square and ramp outputs of my 1222 oscillators into the 1163 mini mixer and noticed that when I turn on both waveforms from the same oscillator, it’s tuning drops.
Any reason for that to happen?
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How are your modules powered? Could it be that there is too much draw? In order to test, unplug the power from all other loads on the power supply and repeat your test.
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No output buffers on 1222, no input buffers on 1163 => some feedback from one output of the 3340 to the other wreaks havok ?
That’s a real question needing an answer…
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maybe solder a 100pf resistor over the top R9 on the mixer it might sort that out!
this situation is usually pretty rare. so I tend to omit things like this for sake of simplicity, hence things like some filters dont have output buffers, decoupling caps only where its obviously needed etc haha. but they are usually in line with other components, so like a feedback filter cap give it a go!
heck you could even solve this problem with using longer patch cables that could stop this too haha :D.
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Theres such a thing?
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hahaha plonker alert, my head was on a resistor order as I wrote that!!! 100pf ceramic capacitor, literally soldered on top of the R9 resistor. so its like piggybacking it
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Knew exactly what Sam meant: a shunt.
Missed the resistor word completely.
Sharp eyes @Vumnoo
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Thanks everyone for the replies!
I’ll try that and report back
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