Forgive my copy-pasting of my original post on several other forums.
I was given this crusty old phaser to repair for a friend. I cannot find any information about it whatsoever as it is of an old era of knockoff pedals.
A pdf of what must be a very similar schematic to this. The same phasing JFETs, buffer, switching circuit and op-amps are used, albeit with some insignificant parts substitutions to cut costs.
There are a few missing parts but they appear to have either been removed cleanly or never installed, as the pads are soldered over and have no cutoffs residing in the holes. Perhaps this PCB was also used for a stereo phaser.
Pressing the switch turns on the LED but does nothing to change the signal whatsoever. As this is a phaser with a signal composing of wet and dry mixed at the output, this must mean the phase signal is either non-existent or blocked somewhere along its path, right?
From my audio probe, it does not seem to be apparent anywhere throughout the pedal, so it would surely be a common issue to each stage. Dry signal is present throughout each of the phase stages.
I am thinking it is either a dodgy common voltage supply to the K30As that do the phasing, or the flip-flop circuit is not correctly turning on the switching transistor, thus not allowing the wet signal to pass.
Does anybody else have any ideas as to what I should test or replace next?
Some images of this relic from a bygone era:
I was given this crusty old phaser to repair for a friend. I cannot find any information about it whatsoever as it is of an old era of knockoff pedals.
A pdf of what must be a very similar schematic to this. The same phasing JFETs, buffer, switching circuit and op-amps are used, albeit with some insignificant parts substitutions to cut costs.
There are a few missing parts but they appear to have either been removed cleanly or never installed, as the pads are soldered over and have no cutoffs residing in the holes. Perhaps this PCB was also used for a stereo phaser.
Pressing the switch turns on the LED but does nothing to change the signal whatsoever. As this is a phaser with a signal composing of wet and dry mixed at the output, this must mean the phase signal is either non-existent or blocked somewhere along its path, right?
From my audio probe, it does not seem to be apparent anywhere throughout the pedal, so it would surely be a common issue to each stage. Dry signal is present throughout each of the phase stages.
I am thinking it is either a dodgy common voltage supply to the K30As that do the phasing, or the flip-flop circuit is not correctly turning on the switching transistor, thus not allowing the wet signal to pass.
Does anybody else have any ideas as to what I should test or replace next?
Some images of this relic from a bygone era: