Question about MXR Phase 90 Pedal

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Just recently had a friend give me a broken mxr phase 90. said that he couldnt get it to power on with a 9v batter and had never tried a power supply. so i just figured that it just needed a new 9v battery cable to be soldered in. well i plug it into my boards power supply (visual sound 1spot) and as soon as i did power to my other pedals was completely cut off. as if the phase 90 was sucking all the juice out of my 1spot. so i quicky unplugged it. as soon as i did all my pedals had power again and nothing seemed to be fried. so does anyone have any idea what could be causing the problem? im pretty good at soldering and i have a basic knowledge of electronics (replace my own volume pots, switches, pickups) so if its just a solder job i should be able to do it. any help is much appreciated.

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This is likely a problem very near the power input connector. It could be a blown filter cap (electrolytic) or a shorted protection diode. You can troubleshoot this with only an ohmmeter.

A broken power input connector could also be causing a short.

Often the input audio connector is used to switch the power on so trace the power circuitry looking for the problem.

Suggestion test seperate from other pedals. Be careful to not burn out your power supply during testing... we put a lamp in series with teh 120 volts to the power supply to limit current to a safe value while troubleshooting.

Posted on Aug 09, 2010

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