Mutron Phaser II - assistance & schematics needed

[Dr Ron]

A friend dropped off a Mutron Phaser II that doesn't phase.

The first issue is the schematic - does anyone have a good one?
The only one I could find is almost unreadable.

My initial guess is the LFO is not oscillating.

There are two trim pots, but I can't read what the notes are on that schematic.

Any assistance would be greatly appreciated!

[Derringer]

http://www.aronnelson.com/gallery/main.php/v/RLBJR65/Mu-Tron+Phasor+II+pg1.GIF.html

and

http://www.aronnelson.com/gallery/main.php/v/RLBJR65/Mu-Tron+Phasor+II+pg2.GIF.html

both conveniently located in the Layouts Gallery

search for "phasor"  with an 'o' not an 'e'


I had similar problems with mine. Replacing ALL of the electrolytics got it up and running again.

good luck

[Gus]

Don't guess measure

Check geofex and do some searches here

Now do you have a DMM and a scope?  Do you know how to signal trace?

First thing with old EH and Mutron and other effects
check solder connections and check for broken wires sometime they look good but are broke inside the PVC.
  Did the board have coffee or soda or beer spilled on? it all will corrode traces and leads.
Then check for voltages at the chips
Then with a scope check the LFO waveform or sometimes DMMs have a bargraph at the bottom you can sometimes use at low frequencies.

I have fixed two 2s.  One was bad connections and the other was bad connections and someone before me tried to fix it and placed wires in the wrong place.  In a number of old effects I fixed, all I did was fix solder and broken connections the old parts were fine.

[Derringer]

you're right, I forgot to add that I did touch up plenty of solder joints in mine as well

[Rodgre]

I have fixed FOUR Mutron Phasor IIs which had the SAME problem.

They didn't phase. On the first one, I accidentally stumbled on the solution. By pressing on the RATE control, it started to sweep again.

Yup. They all had bad solder joints around the rate control. Just reheat them all and swirl away!

Roger

[Dr Ron]

Everyone was spot on ... it turned out to be a bad solder joint on the chip for the LFO, which was hidden under a piece of metal.
I touched the chip and a waveform showed up on the scope.

The effect, however, seems to be quite mild, although extremely cool.
The internal trim pots didn't seem to have any effect.

I'm wondering if this might be how it is supposed to sound.

It's much milder than this Maxon, but similar.
http://maxonfx.com/mp3/pt999.mp3