Anyone have a schematic for the Walco Signal Booster?

[Harry]

Can't remember if I've seen this one before..

[Harry]

Or gut shots?

[FUZZZZzzzz]

I've seen a lot of Walco schematics over the years, but never the Signal booster. There was a time when you could buy them for almost nothing on EBAY. Personal note: I see Thurston Moore uses one on stage. I just love the way it's incorporated in his signal.

[Harry]

Ok, there's a parts listing here:
http://www.diystompboxes.com/smfforum/index.php?topic=5022.0
Leaves us with 5k pot, 1M5, 220k, 4k8, 4.7uf, 4.7uf and 6.3uf to work with.

Taking a stab in the dark here's a guess:

[kaycee]

These used to pop up on Ebay a while back, maybe still do? A guy I do some work for got a set of them, most of them had issues right out of the box (well, blister pack). Components grounding out on the casings, switches falling apart. Typical of the kind of manufacturing that made 'made in China' a standing joke back in the day.

To a box, these things all sounded horrible, the Tremolo ticked like mad, the Sustain thing was particularly hilarious IIRC. Anyhow, build any single transistor booster, its as good as this thing I'd say.

[Harry]

Here's a poor quality shot of the trace side of the kent ea-1 power booster which is very likely the same circuit. You can clearly see the 2 board mounted dpdt sliders. I'm not sure which pins are the tranny legs, though.

[Harry]

These used to pop up on Ebay a while back, maybe still do? A guy I do some work for got a set of them, most of them had issues right out of the box (well, blister pack). Components grounding out on the casings, switches falling apart. Typical of the kind of manufacturing that made 'made in China' a standing joke back in the day.

To a box, these things all sounded horrible, the Tremolo ticked like mad, the Sustain thing was particularly hilarious IIRC. Anyhow, build any single transistor booster, its as good as this thing I'd say.

I haven't used an original, but the worst component selection and nonexistent quality control seems to be their biggest issues. The circuits ARE pretty goofy, but I think that's what makes them interesting and can be modded to be slightly more useable. I've bread boarded the fuzz tone generator and it blends from complete treble removal to an anemic fuzz-rite. I've got the sustainer on the bread board right now and I'm not getting much noise at all surprisingly. Definitely, a psychotic amount of compression and crazy loud :-D. That's what I like about them totally extreme for no good reason.

[kaycee]

Oh yeah, that sustainer thing is FUN. Very much like your description, it swallowed the input signal then regurgitated it on a tidal wave of frying sausages, mental! The one I had was very hissy, worked best with a fuzz input of some kind, it was sort of like a swell effect too. I seem to remember a fair bit of info here and there on that one, but was never interested enough to bread board it myself.

The tremolo was kind of like the Vox repeat percussion, with even more percussion, couldn't shut it up clicking away. Funny little boxes, trust Thurston to use one eh?

[italianguy63]

Ask and you shall receive!!

Front:



Back:



Picked it up on FleaBay.  Doesn't work.  Only pops when you switch the switches.  I am assuming the switches are bad-- they are junk.

Components are:
1M5
480R
22K
5K-B Pot
2x 4.7uF on front
33uF on back
(2S)C828 = BC550

[italianguy63]

Maybe you can return the favor and trace the schematic (w/switches) so I can troubleshoot this thing....

MC

[induction]

Have you tried just replacing the electrolytics? They look a bit ripe.

[italianguy63]

I haven't done anything but try it.. and open it up for the pics...  On my "to do" list now that I got my long term PITA guitar project done.  I just have to restring that beast and it is out of my hair.  This is just a "weird" thing.  I pick up old pedals cheap and resell them when I can.

[Gus]

The switches might be good.

The switches are easy to measure.  With a meter set to ohm place one probe on a center pin you should read open to one of the outside  pins and closed to the other. Then test the other side of the switch

The switches used can sometimes be cleaned by switching them a number of times, be careful using any cleaner

Take voltage measurements of the transistor legs to ground this will help troubleshoot and help with the schematic.

The caps might be fine.

You could have a bad jack/plug this can be checked with a meter set for resistance .   Check the tip to the yellow wire at the PCB, the sleeve to the black wire at the PCB,   Do the same type test for the jack.

[italianguy63]

I just checked the switches while you were typing actually.  Continuity was very limited, and errattic.  Almost certainly they are bad.  I will spray them with some CRC and try again later... They even don't "feel" good when switching them.

[Gus]

Before the CRC try a drop of water and switching them about 50 times.

[kaycee]

Also worth checking things for grounding out. One I had, inserting the jack touched the tip to the pot back. Re-flow everything connection wise too, the wires are hair thin and poorly soldered too.

[Harry]

Wow, thanks Italianguy!!!

Also worth checking things for grounding out. One I had, inserting the jack touched the tip to the pot back. Re-flow everything connection wise too, the wires are hair thin and poorly soldered too.

Yes, I agree it looks like the tip is very close to the back of the pot on his pic.
Here's what I got minus the switching:

[italianguy63]

Just a quick update-- until next time.

Cleaned and worked the switches... refloated all the solder contacts.  They were especially crappy around the switches.

Now it passes some signal, and the pot works.  (it passed nothing before).  More of a tone sucker than a tone booster... Obviously it still has problems.  Back on the "to do" pile until I have more time.

MC

[Harry]

Just a quick update-- until next time.

Cleaned and worked the switches... refloated all the solder contacts.  They were especially crappy around the switches.

Now it passes some signal, and the pot works.  (it passed nothing before).  More of a tone sucker than a tone booster... Obviously it still has problems.  Back on the "to do" pile until I have more time.

MC

Make sure the electrolytics are oriented correctly, from what I've heard these were often installed incorrectly. I'll do my best to describe this in words... The cap on the back of the board (I'm assuming this is the 33uf) should have it's negative side on the ground rail. Ground rail is the the bottom most trace on your second pic. The first cap in your first pic should have it's positive side closest to the 1M5 resistor. The second cap should also have its positive lead facing the 1M5 resistor or the slider switch.
Let me know if there's anyway else I can help. I hope to have this on the breadboard tomorrow and I'll post voltages if it sounds right...

[Harry]

Ok, I have it working on the breadboard. Voltages with a 9.06 battery and a 2sc828a tranny 480 resistor subbed with a 470...
base reads .72v
collector 3.65v
emitter .1v
Here's the 2sc828a datasheet for a pinout in case you want to check yours:
http://html.alldatasheet.com/html-pdf/108448/ETC/2SC828A/54/1/2SC828A.html

I like it, low setting it's fairly clean, slight bass boost. I don't have a lot of experience with boost pedals to know whether the unit is distorting or the preamp but either way it does get LOUD and nasty when you crank it. Could very well be putting out the 40db boost as advertised on the package