Help needed!! Beginner building a positive ground guitar effects pedal. Stuck!!!

Thread Starter

Boxcarwillie

Joined May 8, 2018
1
Hello everyone!

I'm trying to build a wem pep box type pedal with germanium transistors (pnp) which requires a +ve ground circuit.

I've built it according to this circuit diagram:

https://4.bp.blogspot.com/-tbrvn34Bgsw/VdzL-59yEhI/AAAAAAAAF3E/W12fKenBDz8/s1600/WEM%2BPep%2BBox%2B-%2BGermanium.png

Wired the 3PDT footswitch like this:

http://www.tdpri.com/attachments/forumrunner_20121229_091235-jpg.158546/

Wired the tips of the jacks to 'in' and 'out' as per the diagram, then wired the sleeve of the jacks to the ground of the circuit.

I'm sure some of you will laugh but... built the first prototype 'off-board' so to speak! Here's a picture if it helps


I built the second prototype on a perf board, but after having the same result, I amended it to resemble this circuit:

https://www.diystompboxes.com/smfforum/index.php?topic=95765.0

Still no joy. Here's a picture of the second build attempt:



Basically what happens is that you get true bypass whether the circuit is connected to power or not, when you power and switch to the circuit you get a quiet sound of the guitar signal that is totally unaffected by adjusting the pots, and a loud buzzing noise.

I am powering the circuit from a Walrus Audio Phoenix power supply using a reverse polarity cable.

I have tested the transistors with a multimeter - I don't know if there is more advanced testing that can be done? They are NOS from eastern europe. I used different ones on the second build in case the first two happened to be bad.

A lot of head scratching done around the +ve ground issue and whether or not things are connected the right way round, but I tried switching things - for example the direction of the first capacitor is different in the two circuits, so tried that in both directions - no change there.

I used a 50k pot instead of a 500k with a 56k resistor - which is apparently the original configuration - but surely that wouldn't be the problem?

I'm a bit baffled at the moment. Any help would be hugely welcome and appreciated. Thank you!
 

ericgibbs

Joined Jan 29, 2010
9,575
hi Box,
Welcome to AAC,
Is this image from your link the correct circuit.?
E

EDIT:
For a test of the power supply connections, I would power the Pep Box from its own 9V PP3 battery.
Let us know the result.

germaniumpepbox.png
 
Last edited:
Top