Guitar Pedal help

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3MZ
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Guitar Pedal help

Post by 3MZ » Sat Apr 16, 2011 3:44 pm

I have this old MXR Phase 90 from the mid '70s, and I can't get it to work. When the pedal is turned off it will pass the signal through (the guitar is clean sounding) but when you turn it on there's a small amount of static and no guitar signal. If anybody here knows how to start trouble shooting this please help :wink:
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Bush
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Re: Guitar Pedal help

Post by Bush » Sat Apr 16, 2011 9:14 pm

Try opening it up and looking for shorts/burnt fuses etc
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Re: Guitar Pedal help

Post by Snow_Cat » Sat Apr 16, 2011 9:37 pm

Check the rheostat or potentiometer that the pedal actuates.

Sometimes one end of the track breaks.
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3MZ
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Re: Guitar Pedal help

Post by 3MZ » Sun Apr 17, 2011 3:00 pm

I've checked for shorts, etc. obviously, and replaced the potentiometer and switch... I'm fairly certain there is something up with the board itself. How would I check that without just replacing the parts one by one?
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Re: Guitar Pedal help

Post by Snow_Cat » Sun Apr 17, 2011 5:21 pm

Figure out the signal path then with an oscilloscope or damn good multimeter look for the component that the signal is not passing through as expected.
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