Phase II Problems

[Jovi Bon Kenobi]

Finished building this up and it is not producing any effect when activated. When activated and the indicator LED is on I just get my dry guitar signal. There is a very faint ticking sound relative to the rate potentiometers position if it's on or off. As I do with every build, I audited every component for correct value before soldering. I recorded all the voltages on all IC's and the transistor with my DMM. I'll post them in a few minutes but here's the photos.

Oh, and the 2 things I did differently from the build doc is use a 5mm UV LED for the indicator (build doc says 3mm red, is that the fault?!) and also, I used an A50k for the rate because I don't have any A25K's.

 

[zgrav]

this article is a great explanation of how the univibe pedal works (a pedal that has a lot in common with your phaser pedal). you may get lost in it pretty quickly if you try to go through all of it at once, but you can bookmark it and focus on a little bit at a time. it explains what the photoresistors do in the circuit and how the LFO (low frequency oscillator) works. it also sort of walks you through what happens in the circuit, which is useful for knowing where to check things with an audio probe.

Frames for The Technology of the Univibe

www.geofex.com

 

[Jbanks]

Maybe look at a working pedal you have built and the circuit diagram for it, and use your audio probe to learn how to follow the signal through it to get some practice. Then you will have more experience using it to find where something stops working when you are troubleshooting.

I learned to use a audio probe on a really really basic fuzz with about 7 components. You can start touching the probe to the input and output jacks to get a feel of how it works. Just start at the Input jack on the schematic and start following from component to component. On a simple fuzz, it’s straight line without a lot of complications. Once you get the hang the probe, you can begin to trace out more complicated schematics. But it’s a really strong way to follow your signal path and learn how the components add and take away gain/volume/tone etc. if you find a spot with no signal, that’s the problem component.

I always have a looper pedal playing a riff into the pedal so it can just always be sending input signal to the PCB.

But the probes pretty easy to make and is definitely your best tool (besides a DMM) at troubleshooting PCB’s.

Good luck!