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SOLVED Propolis Fuzz just buzzing

Hey all,

This is my first attempt at building a pedal, so sorry if I’ve done something dumb. Current state is when the switch is off, everything is fine (audio makes it to the amp), but as soon as I switch the pedal on, there is a loud buzzing noise and no audio signal (led also lights up). Any idea what might be wrong or how I could troubleshoot it?

Thanks!
JB
 

Attachments

Bumping this up. I've gone back and checked for bad solder joints, and everything seems to be in order, but still just buzzing. Anyone have a suggestion on what I should check?
 

zgrav

Well-known member
I suggest looking at the troubleshooting topics on the forum, especially from folks who are early on the learning curve. You will see good suggestions on steps to take. Those will include taking the PCB out of the enclosure to see if it works, posting pictures of both sides, using your digital multimeter and putting together an audio probe. The encouraging thing is that you will see that most folks following those suggestions are able to share more detailed information, get feedback, and get their pedals working.
 
I suggest looking at the troubleshooting topics on the forum, especially from folks who are early on the learning curve. You will see good suggestions on steps to take. Those will include taking the PCB out of the enclosure to see if it works, posting pictures of both sides, using your digital multimeter and putting together an audio probe. The encouraging thing is that you will see that most folks following those suggestions are able to share more detailed information, get feedback, and get their pedals working.
I suggest looking at the troubleshooting topics on the forum, especially from folks who are early on the learning curve. You will see good suggestions on steps to take. Those will include taking the PCB out of the enclosure to see if it works, posting pictures of both sides, using your digital multimeter and putting together an audio probe. The encouraging thing is that you will see that most folks following those suggestions are able to share more detailed information, get feedback, and get their pedals working.
Thanks, Zgrav. I just built an audio probe (wasn’t familiar before you mentioned), and it seems like I am getting audio until capacitor C1 (a 10uf tantalum capacitor). At C1, I start getting a buzz instead of audio. I double checked the capacitor polarity, and that is correct. I then measured the capacitance of C1 with my multimeter, and it is measured at ~20uf, rather than 10uf that the part is specified at. I got the capacitor from Tayda, and it has a 10% tolerance, so this would seem to be out of spec. Just to build my intuition a bit, is this the expected outcome (i.e. the buzzing sound) for a 10uf capacitor operating at 20uf? Thanks again for your help!
-JB
 

PedalPCB

Administrator
Staff member
Are you measuring the capacitor in-circuit, or did you remove it to measure? You won't get an accurate capacitance measurement in-circuit.

Do you have audio on either side of C1? Or buzz on both sides?

To answer your question though, if the capacitor did actually measure 20uF and wasn't defective (for example, if you installed a healthy 20uF capacitor in that location instead of 10uF) the circuit would still work properly. This wouldn't cause a buzz.
 
Are you measuring the capacitor in-circuit, or did you remove it to measure? You won't get an accurate capacitance measurement in-circuit.

Do you have audio on either side of C1? Or buzz on both sides?

To answer your question though, if the capacitor did actually measure 20uF and wasn't defective (for example, if you installed a healthy 20uF capacitor in that location instead of 10uF) the circuit would still work properly. This wouldn't cause a buzz.
No, buzzing on both sides of C1. I assume I should focus here for now (can be more issues after this, I suppose). Should I check anything else besides the cap value? Here’s the backside of the board for further detail.

Thanks for the tip on not measuring capacitance in circuit. I’ll remove it tomorrow to check it.
 

PedalPCB

Administrator
Staff member
Check for continuity between the top end of R2 and the negative side of C1.

Just to be safe, I would go back over the solder connections for R2 and C1...
 
Update: I’ve narrowed down the issue to R2 (22K resistor). With the audio probe, I get audio on the front side of the resistor, but only buzzing on the back side. I removed the resistor and replaced it, then I tried again withe same result. Next thing I did was to desolder the offending side of the resistor and try the probe on the backside of the resistor while not connected to the board, and I was able to get audio when not connected. I then again tried soldering the resistor to the board and again no audio after R2. My conclusion is that there must be some type of short in the circuit at the back side pad of R2; however, I’m not sure how to determine where the short is. Any thoughts?
 
All,

I have good news and bad news. The good news is, I've identified the problem and the pedal os now working perfectly. The bad news is, as I feared, I was doing something incredibly stupid, so I wanted to share here, in case it helps someone else avoid issues in the future.

The problem was that the power adapter I had lying around was for a Digitech Whammy pedal, and was therefore a 9V AC power supply, rather than 9V DC. I realized this when I got the same buzzing from a new pedal I had just bought.

Thanks to all that contributed on the thread: Chuck, Zgrav, PedalPCB, twebb. I really appreciate your help, and I'm sorry for wasting your time with my blunder.

-JB
 
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