MuTron Phasor 2

[Calypsob]

I have owned this pedal since 2003 and I bought it as is from a studio in L.A.  off of ebay.  Since day one the pedal makes psycho crazy noises if I turn up depth, rate, or feedback too much so I have always used it on slow speeds, even then it will go kind of crazy.  I never took the time to fix it because I started playing bass and intended to fix it one day down the line.  Back then it was hard to find information about this pedal but I have seen alot of stuff about it on this site so I thought I would investigate a bit to see how I can fix my pedal. 

I am not an electrician and have limited knowledge of circuits.  I have multimeters and can test outlets and car batteries, I know how to change a fuse, solder and desolder, and thats about it.  I opened the mutron pedal up today and noticed it has a transformer and 2 capacitors.  Thats when I decided I had better get some professional advice before I go  poking around this pedal spraying contact cleaner and the like.  If anyone could please advise me on discharging the capacitors, and manually adjusting the 10k switch without an oscilloscope, and finding a replacement optical pot, as it seems someone stuck a normal one in the depth control, I would greatly appreciate it.  If I need to give you more information I will be happy to do so.  HEre are some pictures of what I am working with here.


Untitled by LMNO Sunset Deluxe, on Flickr 
Untitled by LMNO Sunset Deluxe, on Flickr 
Untitled by LMNO Sunset Deluxe, on Flickr

[theehman]

I'd check all the pads where the pots are soldered to the board.  The pots just barely reach and under stress the pads will break free from their traces.  I take a small piece of solid wire and stick it in the pad hole, solder it to the pad and the pot lug, then solder the other end along the trace for reinforcement.

[Calypsob]

Ok thats a good tip, the original POTs have pads beneath them, the new looking one in the middle does not.  The pots appear to be in good shape and when in use they do not crackle or pop.  The horrid sound comes from what sounds to me like the LFO or Oscillator unit.  It looses its silky smooth syncronocity and goes into a crazy squelching barking sound which terrifies all animals, my dog instantly peed on the floor when she heard this sound lol. It must be fixed!  I am pretty sure it is the 10k adjustable thing which can be tweaked with a flathead screwdriver, I just need advice on adjusting this and testing it so I do not electrocute myself!  This pedal runs on AC, not DC like new pedals. 

[Calypsob]

The rotatable pot it located in this shot closest to the first 4558
IMG_0904 by LMNO Sunset Deluxe, on Flickr 

[theehman]

I doubt it's the trimpot.  That sets the bias for the oscillation.  I'd look around for a broken solder joint.  Bad solder joints won't cause crackle and pop on the pots but it could cause the Rate or Feedback to go crazy.

[Calypsob]

Yea I'm at a loss, checked all the connections and I don't see anything.  Probably going to sell it as is.  Powers up, works and makes sound but goes crazy if you turn up the knobs too far.

[armdnrdy]

Can you post a sound sample of the problem?

Many forum members would be able to narrow your search and pin point the problem if they heard what the problem is.

While "It looses its silky smooth syncronocity and goes into a crazy squelching barking sound which terrifies all animals" is a funny description, it fails to create a concrete image of the problem so that one might direct you where to look.

[Calypsob]

certainly, thats a great idea.

[theehman]

BTW, those are all standard pots.  There are no "optical pots" in it.  Rereading your description the problem might be just an incorrect replacement pot.