Walco Sustain

[jneely]

Hello

For $20 bucks I couldn't help but check this thing out. I heard it over at tone frenzy and it sounded okay.

I plan to trace the circuit to see if I can work with it on the breadboard.

So far I found it has three NPN trannies and an N-Channel Jfet. It also has a DPDT for true bypass.

This was just after opening it when I got it in the mail.

Has anyone already done this?

Thanks
Jeff

[Arn C.]

Hey man!
   There was a schematic floating around somewhere and I did try it, but couldn't get much out of it-didn't seem to do much of anything.   Maybe transistors have to be matched?  Not sure.  It was a while back when I did it.   Yes, I would like to hear how yours sounds and maybe give it a go again maybe this time with some voltages, some more specs....
Peace!
Arn C.

[Dan N]

Here's from the trace I did awhile back. I had posted one that turned out to be backwards. Rob Strand got it straightened out.

http://users.rio.com/senorris/junk/wcns.gif


This was the original layout:

http://users.rio.com/senorris/junk/wsusmk.gif

[Alex C]

I bought one of these on ebay for $5, but it didn't work when I got it.  I put a 3pdt in there, switched out the jacks, and made it into a LMB minibooster.  Nice small box.  Someone had mentioned that these effects aren't vintage, and I think they're right.   All the ones I've seen for sale say "unopened vintage 70's effect."  I find it hard to believe none were ever opened for 30 years.

Alex

[Paul Perry (Frostwave)]

Just looking at the ckt, nothing needs to be matched, but I think that results will vary according to the cutoff of the 3SK30 fet. Which you might be able to compensate for by fiddling with that 300 ohm emitter resistor in the first 2SC871.

[jneely]

THe schematic trace you did is pretty good but the 3sk30 has two gates. On my unit it meets the grounded end of the two diodes.

The modern equiv is an nte222. I don't think the 3.3m resistors are parallel. I thought one went to the gate of the fet and one to the first trannie. I'll have to look again.

Jeff

[Dan N]

Cool. I figured the extra lead was just a case ground. I got the GSD spots from the markings on the PCB. I'd like to fix the schematic, but don't know what a 2 gate fet symbol looks like.

The 3M3's are kind of sneaky, but they do run parallel.

Dan

[Dan N]

Hopefully this is correct?

http://users.rio.com/senorris/junk/wcnsV2.gif

[petemoore]

First time for everything...
 That 1M5 resistor at input, in the siganl path...What a whoppingly large resistor value compared to anything I've seen in schematics 1, 2 and Links !  ....comments>?

[Eric H]

First time for everything...
 That 1M5 resistor at input, in the siganl path...What a whoppingly large resistor value compared to anything I've seen in schematics 1, 2 and Links !  ....comments>?

I have seen another scheme  like that I believe it was an opamp based pre-amp --I thought the input resistor was a mistake, so I'm curious too.

-Eric

[jneely]

It looks to me like the two three megs meet on one end then one goes to the base of the first tranny.

The second to g1 of the mosfet.

When I check with a a meter it signals this is the case.

Since they aren't both going to the base of the first tranny I'm confused about how they run parrelle ?

Thanks Jeff

[jneely]

It looks as if the 3meg goes to the gate of the fet ?

[Eric H]

Hopefully this is correct?

http://users.rio.com/senorris/junk/wcnsV2.gif

Interesting little circuit.

Well that symbol is a dual-gate mosfet (as is the nte222 sub that was mentioned) too bad Rob isn't around --I missed the original thread. That's the first stompbox I've seen using one of those. The second gate is grounded, though. You can make a one-transistor cascode out of these, and when I mentioned this to Jack Orman about 5 years ago he said he'd tried it and wasn't impressed with the sound, so I dropped the idea. Wonder if they just had a bunch laying around?

-Eric

[Dan N]

It looks to me like the two three megs meet on one end then one goes to the base of the first tranny.

The second to g1 of the mosfet.

When I check with a a meter it signals this is the case.

Since they aren't both going to the base of the first tranny I'm confused about how they run parrelle ?

Thanks Jeff

They both start at the + side of the input cap, and finish on the trace with the gate/collector/10M resistor. Flip your board over and measure across the one on the back. I get just over 1M4.

You know the trannies are ECB?

too bad Rob isn't around

I agree! Rob was sure a great help with a lot of stuff!