Trouble shooting a Mu-Tron Phasor

[Keller]

This not a DIY project, but the actual vintage pedal. It has an AC power cord that is part of the pedal, so I am little bit more intimidated by working on it than a regular 9-18V circuit. I just got it from a friend for free. When plugged in, it powers on, but passed no signal regardless of toggling the bypass switch. I guess my question is, where do I start? I guess cold solder joints are the first culprit? Is it possible that because of the age of the pedal, some of the caps have just given up?

[petemoore]

  Read and apply the information/content in the sticky thread "What to do when it doesn't work".
   AC wall voltage is a danger to work on.

[DavenPaget]

It's possible to work on it if you are very sure it's discharged , it's definitely one of those pedals that require more then one power supply line or an odd power supply line therefore a tranny inside .
You can debug if you have a dual output power supply .

[Mark Hammer]

There will be 3 paths to debug:

1) The straight signal path.  Phasing works by combining two signals, and the clean path is one of them.  Since you report no signal (as opposed to no "effect")  this is clearly the one of primary interest.

2) The phase-shift path.  If one has "signal" but no effect, then there can be a discontinuity somewhere in the phase-shift stages or where they combine with clean signal.

3) The modulation source.  The LFO needs to work AND find its way to what it is modulating for there to be an audible effect.

If you have a meter that can read AC voltages below, say, 2 volts, then one thing you can do is plug your guitar into the unit with the power on, and test for reasonably appropriate AC voltages at various relevant points.  For example, there should be an AC voltage where the switch connects to the board.  There should be a suitable AC voltage on the output pin of the first op-amp stage, and so on.