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Hello all,
First off, can I say the documentation for building this pedal is fantastic! I’d consider myself a moderately experienced pedal kit builder, so I didn’t necessarily need the component explanations but those would have been SO helpful back when I was first getting into electronics!
Onto my issue: I just finished building this kit (serial#ZD3818) and followed all the calibration steps exactly, but when I go to adjust the overall gain, I don’t get any guitar signal coming through the pedal when it’s engaged. If I turn the volume knob all the way up I can hear a slight pulsing high pitched tone that turns into a more of a knocking tone when the wave shape is changed to a square wave. If I plug in a guitar with high output pickups and really attack the strings, I sometimes get a fart-y distorted signal coming through the pedal briefly, but that’s it. I’ve visually gone over the board and I can’t see any of the obvious (bridged solder joints, burned components, leads touching where the shouldn’t, etc). I’m using a one spot wall wart power supply to power the Quaverato.
Any troubleshooting help would be greatly appreciated, thanks!
I just have to ask…are the jumpers soldered properly? Sometimes people accidentally skip that step, or just solder them wrong.
Another thing i wanted to make sure of…are you able to tap out a rhythm on the tap foot switch? …Just to make sure the microcontroller is working properly.
The faint pulsing you hear is probably just the LFO leaking through to the audio or ground path. It’s normal when the volume is all the way up.
Let me know about the jumpers.Thanks for such a speedy response, brach (and on the weekend, no less!). I believe the jumpers are soldered correctly. I bridged the two pads contained within the white rectangular outlines at JP1 – JP4. Just to make sure, I went ahead and reflowed the solder at each one and tested the pedal again; same result. I am able to tap out a rhythm with the tap tempo foot switch and the green LED pulses to match that tempo, so I believe the microcontroller is working.
I really appreciate you taking the time to help me troubleshoot!
Ok, good.
Now check to see if the LEDs in each optocoupler are working by making a tiny incision on the heat shrink close to the LED’s leads….just a tiny cut, no bigger than 1mm long…just enough to see if the LED is working.
Let me know what you find.
-BrachThe LEDs in both optocouplers appear to be lighting up and pulsing at the same rate as the status LED on the faceplate.
That was quick.
So that tells us that the digital side of things is working properly, so we know the issue is with the analog circuit.
When you turn the gain trimpot up all the way (counter clockwise) do you notice the LFO noise getting louder? I’m just trying to see if that component/part of the circuit is working properly.
It would also be helpful to know the DC voltages of all 14 pins on the TL074, with the depth knob all the way down and no audio signal in the input jack.
By the way, do you hear the relay click when you press the bypass foot switch?
Thanks and good luck.
I probably won’t be able to respond more until tomorrow or monday.
-BrachThe volume of the LFO noise does NOT get louder as I turn the gain trimpot counter clockwise.
Here are the voltages at each pin of the TL074 (which I’ll admit, I deviated slightly from the kit on, and installed in a 14-pin DIP socket) with the depth knob turned completely counter-clockwise and a guitar cable with nothing plugged in on the opposite end inserted into the input jack with the pedal engaged:
1: 1.65
2: 1.65
3: 1.46
4: 9.34
5: 0.97
6: 1.46
7: 1.46
8: 8.67
9: 5.59
10: 0
11: 0
12: 0.16
13: 8.47
14: 8.47Yes, I can hear the relay actuating when the bypass footswitch is pressed.
Totally fine about your response time, I’m just appreciative for any help at all. I was not actually expecting any response at all to this thread until maybe sometime next week. 🙂
Thanks again!
The problem seems to be with your bias voltage (called V/2 in the schematic). Pin 10 is directly connected to V/2 and you measured that voltage to be 0V, it should be half of the power supply voltage (9V/2)…around 4.5V. You can see the bias network in the center of the page on the schematic…it’s a voltage divider consisting of R10 and R9, along with C15, C10, C11, and C16. Make sure the pins of C15 aren’t bridged. Also make sure none of the other pins are bridged to anything and everything is soldered correctly.
-BrachDang man, you nailed it, haha! I pulled the board from the enclosure and sure enough, C15’s leads were ever-so-slightly bridged. After taking care of that the pedal sprang to life. Sounds fantastic too! Thanks so much for taking the time out of your weekend to help me figure this out, Brach!
Having my current problems be relevant to this thread, I do want to ask here this question how to test the TL074 with the multimeter as I’m new to using one and the desired position of the knobs on the pedal as well as where the leads of the multimeter are positioned? I see pin 1 is marked with the little dot, however my readings are just not even close to what he got as I use this for a reference point…happy weekend!
Richard,
His readings were way off. Use the troubleshooting guide voltages for the correct values (found under the “documents” tab of the Quaverato page on our site”.
To use a multimeter to measure DC voltage (all the voltages to measure on the Quaverato are DC) first make sure the meter is set to the DC voltage (V) setting, not milivolts (mV) (if your meter has a “mV” setting).
Put the black probe (the negative probe) on a 0 volt point in the circuit…we call this the circuit “ground” or “common”. You can use the fist pin of the input or output jacks (the pin closest to the part of the jack with the hole for the guitar cable). Or you can use the point on the pcb that the ground lug wire is soldered to.
Put the red probe on the point you want to test. The voltage difference between these 2 points will be given by the meter.
When you test the voltages on the pins of the IC make sure to not be touching 2 pins at once. Place your red probe on the IC pins right where it comes out of the IC’s body. Make sure the depth knob is all the way counter clockwise. That’s the only knob that needs to be in a particular position.
Good luck!
-Brach
