MXR Phase 90

[rgorke]

I just picked up a block logo Phase 90 that looks pretty old. The guy on Craigslist (or at least his wife with whom I dealt with) says it just stopped working. I haven't had a chance to get it home to poke at it with a DVM. Any thoughts?

Pots are labeled: MXR9479 and 137782

Here is a pic. I took all the decomposed foam crap off.

[vanhalen5150]

Thats the transition from the carbon film to metal film era. The old MXR's wires also have a tendancy to corrosion at the solder ends. Lift the board and look. You may also see one has fallen off. Some of the wires actually turn green under the insulation.

[rgorke]

I cleaned it up and it seems to work. Now I need a replacement for the foam.

[jnewlyn]

Good job there rgorke. I was gonna suggest that resistor at the top of the photo. It looks hammered but since you got it working now, it must be OK. How does it sound.

I bought a JOYO vintage phaser which are cheap and I tell you what. It's really, really good. Not sure of its placement in the chain but I'm going guitar-phaser-MXR-6 band-EPos-3 shitbox thingy to the amp and it's good, good, good.

[rgorke]

James,

It appears that the switch might be bad. I can get it to work but switching on and off seems problematic. So....I have now put it not its own bypass loop and shazaam, works like a charm.

I am also amazed at how much of a boost there is with this pedal.

Guitar, planger, faser, MXR EQ, Echoplex, amp.

Dutch treat,


Roger

[jnewlyn]

Nicely done.

Yeah, I've got this little trim pot inside my phaser. I've never tweaked it but I often wonder what it does. Curious to know if it would boost/cut if I monkeyed with it.

[spaceace76]

that trim pot biases an FET in the circuit. turning it one way or another will make it only "phase" certain frequencies. set up from the factory it works on most guitar frequencies, you can tune it to more bass or more treble if you like that sound, but it can be difficult to rebias without a multimeter, IIRC

[jnewlyn]

that trim pot biases an FET in the circuit. turning it one way or another will make it only "phase" certain frequencies. set up from the factory it works on most guitar frequencies, you can tune it to more bass or more treble if you like that sound, but it can be difficult to rebias without a multimeter, IIRC

REALLY? That's awesome to know. The only thing I've wanted to do with this is just try and change or shift the phased frequencies towards the higher end a bit. So I can do that with that stupid little trimmer? How cool. My thinking is as I shift higher, it will make the effect more subtle. We'll see.