Problems With GuitarPCB.com Mastodon Fuzz

[stevexc]

Newb here, hope I'm doing this correctly.

So I'm having trouble with my very first pedal build. It's the GuitarPCB.com Mastodon Fuzz. I've built it as per the schematics using the GuitarPCB.com 3PDT Wiring Board, in which I've used a 2k2 resistor as the CLR. Everything else is to spec, aside from the battery snap which I've omitted due to space restrictions.

What's happening is when the effect is powered/disengaged I get a very loud buzzing noise but no guitar signal. When engaged I get the effected signal, but the hum is still present although manageable. The hum is not affected by any of the controls on the pedal.

The weird thing is I only get this issue when the pedal "guts" are outside of the enclosure - or at least, when the output jack is not attached to the enclosure. When everything is in the enclosure I get no signal (or noise) whatsoever.



CLR (2.2k) has been added since the above picture, but all that did was allow the LED to work - no change to the actual issue.



The issue occurs with multiple power supplies.

Any help or advice would be much appreciated!

[Aph]

Hard to tell by the pictures, but maybe your wiring to the output jack is reversed...

(PS Welcome to the forum!)

[stevexc]

Thanks for the welcome!

It looks like that was the case, and I am now getting clean signal (with a minimal buzzing sound). However I am getting no signal at all while the pedal is engaged.

[Aph]

Once again, it's hard to tell from the pictures if the wiring is correct.
Make sure the input jack is also wired correctly; the grounds go to ground connections on the boards; that you are getting +9v to the circuit board, etc.

[sixthfloor]

Steve, by no signal at all while the pedal is engaged do you mean no signal and no hum ? If it were the case, check the 3PDT wiring. The output might be sent to ground when the effect is engaged.

[stevexc]

I don't know what exactly I've done (aside from resoldering a few broken wires from moving components in and out of the enclosure) but I'm getting a very good clean signal with no hum now. Still no effected signal.

Once again, it's hard to tell from the pictures if the wiring is correct.
Make sure the input jack is also wired correctly; the grounds go to ground connections on the boards; that you are getting +9v to the circuit board, etc.

Well as far as I can tell the wiring is right, ground is to sleeve on both Input and Output jacks and signal to tip. Checking with my DMM I'm getting voltage throughout the board where appropriate (I can provide measurements if needed). And as far as I can tell ground is going to the right spots, as the PCB grounds are all labelled. The only thing I can think of is both the input and output jacks are wired backwards.

Steve, by no signal at all while the pedal is engaged do you mean no signal and no hum ? If it were the case, check the 3PDT wiring. The output might be sent to ground when the effect is engaged.

That's correct, although I'm now getting no hum on the clean signal as well. I don't know if there's much I can do about the 3PDT wiring as it's through a dedicated PCB.

[sominka]

Disconnect the board from the foot switch etc so you have just the board with In, Out, GND and 9v leads attached. Now you can test it properly using a breadboard or build a simple testing rig. You don't have to but it saves a lot of bother.
All wires connected to GND connect together including the jack GND's. The In lead connects to jack tip In. Out lead connect to jack tip Out. 9v goes to + power supply. The - supply goes to GND with all the other GND's.
See if it works then without the switching. Sorry if you already know this but I personally always test the effect before even considering boxing it up to completion.
You wont have problems desoldering the switch etc if you invest in a solder sucker.

[bloxstompboxes]

In your picture it looks like the input wire tab on the jack may have been touching your enclosure sending your guitar signal to GND. That would explain the buzz and lack of signal on or off with your wiring reversed too. As far as your current issue, we may need to see some schematic and voltage readings as shown on the what to do when it doesn't work page.

[stevexc]

It took a bit of time but I got the board isolated. Still no effected signal. Here's the measurements I'm getting with the black probe on the power jack's ground:

Power jack, + to -: 9.38v
D1: P0 N9.38
Q1: E0 B0.62 C1.33
Q2: E0.7 B1.32 C2.27
Board +9v: 9.38

In continuity mode I'm getting continuity across the board (ie from board In to board Out, as well as from input jack tip to output jack tip). What else should I be measuring?

EDIT: As soon as I have an opportunity to do so I'm going to put together an audio probe to do further troubleshooting. Appreciate the help so far!

[stevexc]

Big update: It works!

Turns out there was a tiny bridge between the PCB output and what I thought was another output hole - but turned out to be an unmarked ground. Fixed that and everything works perfectly!

I have to make a huuuuge recommendation to anyone with a similar issue to BUILD A DANG AUDIO PROBE. Saves so much headache trying to find the source of the issue when you can actually hear it.

Thanks again for the assistance guys!

[bluebunny]

I have to make a huuuuge recommendation to anyone with a similar issue to BUILD A DANG AUDIO PROBE.

Such wisdom after only five posts!       Good advice.