Walco Chord and Note Sustainer Modifications...Help?

I have a couple of Walco Chord and Note Sustainers that I have been tweaking and modifying.

For anybody who has one, they know that out of the box, these things are noisey as can be and unpredictable.

To get rid of a good portion of the noise, I replaced the crazy 3sk30 FET with a 2n5457.

I also needed to file off part of the circuit board to allow for room for the battery to fit. It was suggested to me that batteries might have been smaller 30 years ago when this pedal was built.

The switch is a piece of junk, but I haven't gotten around to replacing it yet.

My biggest concern with the pedal as it stands now is the sustainer circuitry. It is all based around the 2sc644 transistor. I'll post a schematic at the end of the post.

Basically the signal is amplified through the FET and the two 2sc871 transistors and part of the signal is fed back via the diodes and 33uf cap into the base of the 2sc644 which shunts some of the signal to ground when the transistor begins to conduct.

However, when you initially hit the strings with a lot of force the signal completely drops out and slowly comes on like a reverse tape kind of effect. I'm trying to minimize this. Any ideas?

I was thinking maybe a different transistor with a lower gain (the 2sc644 I took out of one of the units measured an hfe off close to 500) or possibly a resistor in series with the collector would help correct the problem but before I go ahead with this, I was hoping for a bit of input.

-Zach Omega

I just found one of these, that some one had gutted for parts, the output jack had been removed, and I wanted to see if I had rewired it up properly. Should the yellow wire from the foot switch be going to the tip and the black ground from the input and battery go to the sleeve, or was this a switching jack? Any help would be wonderful I want to hear how noisly bad this pedal is. thanks Barry

Maybe try putting a pot between the 2sc44 and where it feeds back to the FET input. This way you could vary the amount of feedback with variable resistance. you can try different pot values till you find the one that works best. You could then use a trimmer pot and set it ore replace the amount of resistance the pot reads with a hard resistor if you havent got the space. You can also try it on the other side of the feedback circuit but I'd think unloading the input would sound better.