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mxr phase 90 no sound

Started by copachino, February 12, 2015, 09:54:46 PM

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copachino

hi all i have a hand wired phase 90 from mxr but i cant get any sound of it, not in bypass or fx on, the switch works fine but i get no sound, not noise not nothing, batery its ok and got voltage on the board, any idea wher i shoud start looking first?
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jimilee

With an audio probe, start at the input and go from there. I'm guessing the led lights up?
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mgwhit

I don't think this has an LED and I also don't think it's true bypass, but it's a single-sided circuit board, so you should be able to trace the circuit and the audio path very easily.  Before you even start tracing audio, though, check your voltages on all of your 741 op amps.  You should have about 9V on all pin 7s and ground on all pin 4s.  Pins 2, 3 and 6 should be around 4.5, except on one IC, which is is functioning as an oscillator.  I wouldn't get hung up on the pins, though, as long as the ICs are getting 9V and ground, and the JFETs aren't even necessary to get dry signal.  If the board is getting correct power, figure out how that switch works and test continuity to the board and the jacks.  It's much more likely to be a bad off-board connection than a bad component.  Good luck!