MXR Phase 90 not working

ahh I loved this pedal but now it doesn't work.
by accident I have plugged my adapter which is reverse polarity than the pedal needs. so the led just turned on for a second and then turned off. after that pedal doesn't work at all of course, when in the bypass mode there is signal but when I turn it ON there's no sound. it doesn't work when I run it on battery either.
any clue what it might be?

ahh I loved this pedal but now it doesn't work.
by accident I have plugged my adapter which is reverse polarity than the pedal needs. so the led just turned on for a second and then turned off. after that pedal doesn't work at all of course, when in the bypass mode there is signal but when I turn it ON there's no sound. it doesn't work when I run it on battery either.
any clue what it might be?

There is a small signal diode (1n914 or 1n4148) that is installed reverse polarity to the power supply to prevent damage in case of inserting the wrong adapter. This would be the first place to start. Just after the adapter input jack is a small value resistor, typically 51 ohms. Since the diode would be forward biased with the wrong adapter plugged in, the resistor may have been burned up from the current draw of the diode. Or, the diode may have shorted, in which case the resistor will limit the amount of current draw through the diode. In the first case (the more likely one) the resistor is open, allowing no current flow. In the second, the current is shunted away from the circuit. The two have the same result- an inoperative pedal.

wow thanks a lot! if I won't be able to repair it by myself I'll just take it to technician. hopefully it's not some big failure.

Montana_Dawg can you help me a bit more?! or anyone else please..
I'm totally noob about this stuff but this is what I figured out...
somewhere I read I can test the two diodes next to adapter plug in by measuring the resistance. so I did that and here's the result:
when measuring with analog multimeter the 1st diode gets the needle into the position of ~4k ohms and in other direction it goes into 0... like it should be.
now, when I measure the 2nd diode the pointer on multimeter goes into 0 in both cases. is the 2nd diode invalid then?
here's a pic (btw 1st diode is a bit bigger than the other one)

http://i28.tinypic.com/50i2iq.jpg

Montana_Dawg can you help me a bit more?! or anyone else please..
I'm totally noob about this stuff but this is what I figured out...
somewhere I read I can test the two diodes next to adapter plug in by measuring the resistance. so I did that and here's the result:
when measuring with analog multimeter the 1st diode gets the needle into the position of ~4k ohms and in other direction it goes into 0... like it should be.
now, when I measure the 2nd diode the pointer on multimeter goes into 0 in both cases. is the 2nd diode invalid then?
here's a pic (btw 1st diode is a bit bigger than the other one)

http://i28.tinypic.com/50i2iq.jpg

The larger diode is a Zener diode used to clamp the voltage to a 3V reference.

Are the readings a "0", or an open?

Both diodes are in parallel, and in one direction both would read as an open, where in the other direction, there would be resistance on both diodes. In other words, the reading should be the same for both diodes.

The zener will only conduct when voltage greater than 3V is applied. The other diode will only conduct if the wrong polarity is applied.

actually it's 0. here, I made a quick vid, take a look :wink:

http://www.youtube.com/watch?v=M_eAdBaOaaA

actually it's 0. here, I made a quick vid, take a look :wink:

http://www.youtube.com/watch?v=M_eAdBaOaaA

Okay, I have done some research. I don't have a schematic of the newer Phase 90s, but from photos of both the front and back, the 10k resistor is in series with the diode.

Judging from your video, the small signal diode is shorted, which is one of the cases I gave earlier. With it shorted, the signal is shunted through the 10K resistor to ground. This drops all the voltage across the resistor, so the Zener cannot clamp to the reference voltage. The resistor also limits the amount of current being drawn to ground, which protects the power source.

The small diode is pretty standard, like a 1n4148 or equivalent. Clipping one end to break the circuit should take away the short, and the pedal should function. However, the diode needs to be replaced to prevent the circuit from being damaged if the same situation happens again.

wow, now I got it!! that was a great explanation. so I'll just buy new 1n4148 diode on thursday and replace it. I'll let you know the result.
I really appreciate your effort,
thanks a bunch!

IT WORKS!!!!! thank you Montana Dawg... if you ever come to Croatia, you got beer! :lol: