Question about MXR Phase 90 Pedal

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MXR phase 90 swtiches on but I have no phasing

It has always worked fine and I have had 3 of these pedals now (1st tow stolen at gigs!) So to conclude, I have a clean signal, then I switch on and it makes a sound as if its stuck in one position but no oscilation

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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.

Posted on Mar 29, 2014

Testimonial: "Thanks for your response, its running on AC all the time!"

  • 3 more comments 
  • Andy Karamallakis
    Andy Karamallakis Mar 29, 2014

    Hi Joe, thanks fpor responding, its running on mains though??

  • Joe Patch
    Joe Patch Mar 29, 2014

    What do you mean by this? Is it on battery power?It has a mono in and out. On mains? I may can help if you give me more info on your rig.

  • Joe Patch
    Joe Patch Apr 03, 2014

    Always on AC, the only way to go. Pedals usually are not worth fixing being that it is so hard to find the schematics, if able to find one at all. The only way I can think to help is to look inside for a bad filter capacitor. It should look like a small can standing upright on the board. They are usually gray, blue, or black but, sometimes white or silver. Most of them have a line or an X on the top of it etched into it, weakening the surface to allow it to crack open in case of a failure. This allows the germanium to escape and dry out. These filters are there to block out the noise that you have. If you see any of them cracked open, on the top, side, or bottom, that would be your problem. If you can replace one, make sure the polarity is correct.

  • Andy Karamallakis
    Andy Karamallakis Apr 08, 2014

    Thanks Joe, its part of a pedal board using a DC brick. I think Im going to try my local guitar repair man but if its an expensive fix ill sell for parts and buy new!

  • Joe Patch
    Joe Patch Apr 10, 2014

    Please let me know since this pedal is a dinosaur for effects. It is a nice effect but a dinosaur. You should move to rack stuff if you have used 3 of them. That tells me you never got better in how many years? Really? You would waiste you time and money on that one effect, come on. You should upgrade at least every 15 years at least. Think about that as a player. I use rack stuff but, I can get that effect with no problem with my rack. Are you a pro or an amateur.? Play that thing man.



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SOURCE: MXR Phase 90 doesn't phase only clean signal

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

Posted on May 06, 2010

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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

I'm experiencing an unwanted gain boost when using this pedal

If using another pedal in the loop, change the orrder

Aug 21, 2010 | MXR Phase 90 Pedal

1 Answer

Is there some sort of trim pot or something in the block letter phase 90 where I can turn the volume boost down when it's on. I don't hate the sound of it but it gives me too much gain when I click it. I...

Have you tried experimenting with the order of your signal chain? Have a look at this link:

Jul 02, 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

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

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.

Sep 12, 2009 | MXR Phase 90 Pedal

5 Answers

The correct order for Effects pedals.

Personally, I like to have all "tone effects", such as wahs, distortions and equalizers in front of "time effects" such as phasers, chorus, flangers and delays. See my set up in the photo. Guitar input is from right to left, starting with the wah pedal.
Tom, 30yr player


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