Question about MXR Phase 90 Pedal

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Mxr phase 90 block logo and the 9v power jack not working

I bought a used Mxr phase 90 block logo and the 9v power jack doesnt seem to work please help

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These break and SOMETIMES the circuit board gets cracked.

Open up and inspect for damage. If board is cracked, bridge broken traces by soldering wires around the break.

If the solder is broken, resolder it.

If the connector is damaged or weak spring, replace the connector.

Posted on Sep 12, 2009


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1 Answer

MXR phase 90 swtiches on but I have no phasing

I would check the difference in sound between using an AC adapter and a battery. These things lose the effect when the batteries get low.

Mar 28, 2014 | MXR Phase 90 Pedal

1 Answer

I just bought an MXR Phase 90 and i do not have the right 9v cable to plug in to the wall. So i just bought a duracell 9v battery and pluged it in. When the pedal is bypassed i can hear the gutair through...

The battery is being shorted by something. It is impossible for me to guess what without looking at it. If the pedal is brand new, take it back for warranty repair/replacement. If you bought it from somebody, you bought THEIR problem... they likely knew about it. If this is the case, look for a pinched wire from the battery lead... make sure it is not backward. If you can't see anything and cannot get a refund, open the pedal. Look for a problem where the 9 volt adapter plugss in. Broken jack, etc. Look for evidence that somebody has taampered with the insides. Of course look for foreign debris.

May 06, 2011 | MXR Phase 90 Pedal

1 Answer

I have the MXR EVH Phase 90. When plugged in, and unit is off my sound is fine. When unit is activated, the light comes on but there is no sound. The same thing is going on with my Maxon AD999 Delay pedal....

The fact that it happens with 2 different units may point to something in common. You just first eleminate the cables as a possibility by swapping. Also, most pedal problems can be traced to a battery issue, so make sure it is a good one. Make sure you are using mono, not stereo cables.

The footswitch could be faulty, try holding it in different ways to see if it makes contact.

Feb 27, 2011 | MXR Phase 90 Pedal

1 Answer

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...

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.

Aug 08, 2010 | MXR Phase 90 Pedal

1 Answer

How do I fix a mxr phase 90 (overvoltaged!with 12V universal)

My first guess would be that the zener diode is probably shorted. Also check the 2N4125 transistor for a short. Start there and update this with your results.


Apr 30, 2010 | MXR Phase 90 Pedal

2 Answers

Bypass is fine, LED lights when active, but signal is very low in volume when effect is active. Almost inaudible.

Make sure power voltage is adequate. If using a battery, the LED will light LONG after the batteery is beyond usability.

Jan 17, 2010 | MXR Phase 90 Pedal

1 Answer

MXR Phase 90 doesn't phase only clean signal. The oscillator is working and I have changed the BJT's.

sounds like a switch contact problem, try some surgical alcohol. (for the MXR not for you!!!)

Dec 31, 2009 | MXR Phase 90 Pedal

1 Answer

Phase 90 dead no led no nothing- it has tl062 and a tl064 chips block script, switch seems good on VOM, can the 2 diodes after the power input be likely problems? I can also swap out the IC chips for...

One needs to consider the history of the unit. Could someone have used a reversed power adapter? If so they probably blew those diodes.

Input power protection diodes are often in the 1N4004 family.

Do not change any diodes without knowing the type. There may be Zeners as part of the effect shaping.

Check the power getting to the Op amps... pin 8 and 4 are the power pins, 8 being positive. Don't get fooled as sometimes the circuitry has the positive as signal ground.

ONLY SHOTGUN a device as last resort.

Dec 11, 2009 | MXR Phase 90 Pedal

1 Answer

Turns on, led works, just suddenly stopped applying its awesome phase 90 effect though.

If you are using battery power, just because the LED lights doesn't mean the battery is adequate. Check the battery voltage.

If you are on adapter power, make sure any bypass switch is in right state. Also occassionally someone gets the in's and out's cables backward... that can do it!

Nov 09, 2009 | MXR Custom Shop Phase 90 Led

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