Hi all, someone help me to understand why my PITCH and WF(wave form) potentiometers are not working, I have built a eurorack module using this circuit on a stripboard (where I found this schematic - they tested it and assured me it worked), when testing I found out that these potentiometers do not work, I checked the circuit and layout many times but did not find any errors, I connected everything correctly, checked all transistors, diodes, chips, all connections and holes, and did not find any error, help me to identify it, please!
This is my first time transferring a circuit to a stripboard, so I may have done something wrong, I want to make sure I transferred the circuit correctly.
That’s a fairly complex stripboard layout, an unfamiliar schematic, and a very vague description of what is wrong (“the potentiometers don’t work”). Asking people to debug such a thing is a lot.
You need to provide some more info about what is working and what is not working.
Is there any sound being produced at all? Under what circumstances is this the case?
Does the envelope generator do anything if you send it a pulse, e.g. does the led respond to an input pulse? Can you see the envelope generator’s output signal on the base of Q7 (or hear it using an audio probe)?
I encourage you to look into how to make an audio probe, it is dead simple (you only need a capacitor, some wire and an amplifier) and try to use it as a diagnostic instrument. Try it on something that works first.
Does the VCA work? You can test this by injecting a signal via a capacitor on the base of Q5, you should then hear something on the output if you send a trigger pulse to TRIG IN 1 (provided that is working)? Or inject a signal on the collector of Q5 OR the collector of Q6 via a capacitor (1uF should be enough). This may help in checking IC5’s working.
It can be helpful if we know what kind of test equipment you have.
Do you have an oscilloscope at your disposal, an analog or digital voltmeter? An audio probe?
Can you hear anything on the output of IC3 pin 1, or IC4 pin 7 and IC4 pin 1?
Thanks for the recommendations!
I only have a multimeter.
On the output there is a sound when the trigger signal is applied, potentiometers “Filter”, “MIX”, “Decay”, “LVL”, LED - work properly, the noise is also heard when turning the potentiometer “MIX”, if the noise is removed - some sound is also heard, I hope on the video it can be heard, the only problem is that the module does not respond to measurements “Pitch” and , “WaveForm”, the rest works as expected.
I can conclude that the VCA is working. Also when connecting the output of the module (without trigger signal) to the mixer, a noise is heard, but it is not the noise of the noise generator.
Thanks for the answer and tips, this is my first experience on the forum, I will take your advice, I’ve uploaded the video below and tried to describe the problem in more detail.
Hmm, it is a bit much for me to try and follow all the wiring on the strip board and compare it to the schematic. I leave that up to you.
However if most is working already, you should be able to check the wiring on the strip board of the stuff that is not working by comparing it to the schematic. I would advise you to use the schematic as your ‘ground truth’, not some stripboard that someone has made. You can use your multimeter in continuity setting or set it to measuring resistance, to check the connections on the path from Q3 via IC3 to Q7. The meter should beep or you should see a very low resistance value (< 1 Ohm).
Note: make sure to check the cuts in the tracks below the IC’s and in other places. There should be no continuity there.
I get the impression that your DEC pot is wired backward, I would expect the decay time to go up in time when turing it to the right. The same goes for the VOL pot, it seems to decrease the volume when turned to the right, I would expect the opposite.
Note: if you set the resonance very high, maybe the change in waveform is not that audible because the main thing you hear is sine-like resonance? I’m not sure this is a factor as I do not know the circuit that well.
That’s the thing that I have already checked the correctness of the circuit assembly, chips, transistors, diodes, dialed many times, wiring, I have only doubts in the correctness of understanding the transfer of the circuit on stripboard as I did it for the first time, so I asked for help in checking the stripboard.
Maybe someone will have time to check and our community will have another interesting drum module on the stripboard.
