This is a wiki post; please correct and improve!
This is written regarding the 1222 Performance Oscillator module, but similar things apply to the simple stripboard oscillator or other oscillators based on the 3340 chip. For the stripboard version also see
If you are not getting good tones from the oscillator, do the following. If with the 1222 you are also not getting good behavior from the tuner, don’t waste time on trying to fix that yet. Get good tones on the outputs first — the tuner won’t behave nicely until you do.
Start with the usual generic troubleshooting procedures:
After that, check if you have 4.0V from the TP1 test point to ground. If not, do this:
(By the way, R42 shown there is specified as 220 ohms but it really should be higher; 220R results in too much current through the voltage reference U4, potentially causing bad behavior and possibly damaging U4 permanently. If you used 220R this would be a good time to replace it with something between 1k and 4.7k. For more on this and other mods see 1222 Tuner VCO Module and 1222 Tuner VCO Module fixes/improvements .)
Once you have 4.0V at TP1, check your control voltages. Do this:
The center note trimmer should have +12V on one end (measured between there and ground), 0V on the other, and something between 0V and +12V on the center terminal, depending on the trimmer position.
The fine tune pot should have +1V on one end, 0V on the other, and something between 0V and +1V on the center terminal, depending on the knob position.
The octave selector switch should have +4V on one end, 0V on the other, and 0V, 1V, 2V, 3V, or 4V on the center terminal, depending on the knob position.
With nothing plugged in, the 1 V/oct and CV input jacks should have 0V on the sleeve terminal and nothing on the tip terminal.
Adjust the center note trimmer; somewhere in the middle of its range you should get an audible tone.
If all voltages are correct and you still don’t have good outputs, go back to the start and double check everything. If it still isn’t working, you could have a bad chip; try replacing the ICs one at a time. If that doesn’t work, post a query to 1222 Tuner VCO Module . (Please don’t post queries to this topic; solutions, yes, queries, no.)