Hey everyone. I decided to dip my toes into pedal building, and decided to start with a Mudbunny 2020.
The actual build went pretty quickly and smoothy, until I ran out of my favorite solder, and found some Bernzomatic rosin core in my supplies that I ended up not liking at all. But I finished everything, and after reflowing some joints I got the board LED to light up.
I plugged it into my amp, and there is a lot of noise with it off, which should have been bypassed. The noise increases with the Volume, and alter with the Sustain and Tone pots. When I turn it on, it makes a constant loud whine that modulates with the Volume, Sustain, and Tone pots.
Here's a video of the noise and whine.
https://youtu.be/xZmly0GMrAY
I took a look at all the solder joints and reflowed some that seemed dull, and checked continuity, but no dice. I'm pretty much stuck, and have no idea how to fix this.
Here's the voltage measurements:
DC +: 8.75 V from the wall wart
All transistors are 2n5088.
Q1
C: 4.036
B: 0.635
E: 37.5 mV
Q2
C: 4.05
B: 0.634
E: 37.4 mV
Q3
C: 3.98
B: 0.63
E: 37.8 mV
Q4
C: 4.774
B: 1.44
E: 0.862
I feel like your stomp board is upside down. The square should be pin one, so all of your wiring is reversed. It's hard to see what's going o without seeing the other side of the stomp board. It would just be a matter of rewiring the board if it is backwards.
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It's a wiring board from Stompbox Parts: https://stompboxparts.com/pcbs/wiring-board-for-3pdt-footswitches/ (https://stompboxparts.com/pcbs/wiring-board-for-3pdt-footswitches/).
1. Input signal to FX PCB
2. Input signal from input jack
3. Ground
4. Output signal from FX PCB
5. LED
6. Output signal to output jack
7. Ground
The connection from the PCB is:
GND -> 3. Ground
L -> 5. LED
IN -> 1. Input signal to FX PCB
J1 -> 2. Input signal from input jack
OUT -> 4. Output signal from FX PCB
J2 -> 6. Output signal to output jack
I'm gonna go with a stomp board problem too. If you can, just wire the in/out/9v/ground wires to the jacks and power, bypassing the switch altogether.
Here's a front side view of the switch/wiring board.
I labeled the wiring board with all the pin connections. I'm pretty sure this is correctly wired. When the switch is on, the top row is connected:
J1 -> IN (input jack connects to pcb input)
L -> GND (turns on LED)
OUT -> J2 (pcb output to output jack)
When it's off:
J1 -> J2 (full bypass of input jack to output jack)
What we're saying is, the square is pin one, you have it on pin seven.
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I'm super confused. Nothing is connected to pin 7 on the switch board. See the front side pic above. https://www.madbeanpedals.com/forum/index.php?topic=33728.msg323983#msg323983
Pin (Lug) 7 on the stomp switch is what I'm talking about, sorry for the confusion. Pad 7 on the stomp board is a ground. Lug 7 is the effect out.
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Thanks for all your help, I do appreciate it.
I rotated the switch 180 and resoldered it. I checked with a multimeter, and the switch seems to me to be working correctly.
ON
J1 -> IN
OUT -> J2
L -> GND
OFF
J1 -> J2
IN -> GND
But.... Didn't make a difference, as the whine and modulated theremin sound is still there. So back to square 1.
To rule out any issues with the switch, desolder or cut the wires, and just hot wire together the J1 to In, and J2 to Out. See if it works like that? But based on your measurements it seems like the switch is doing what it should.
Next step might be to make an audio probe (it's easier than it sounds) and work your way through the circuit to see where it gets noisy.
First thing I'd check is whether you've accidentally soldered the input or output jack wires backwards - tip to sleeve or something like that. I know I've done that before!