WEM, Watkins, Rush - Pepbox, Rush Pep Box  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Electric Warrior
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Post by Electric Warrior »

I believe this one deserves its own thread.
Pictures can be found here: http://www.effectsdatabase.com/model/wem/rushpepbox

This is what I've gathered so far:
C1: 12.5µF electrolytic
C2: 12.5 µF electrolytic
C3: 0.01µF (?), styroflex
C4: ?, styroflex, larger physical size than C3
R1: 1M
R2: 1k5
R3: 100Ω
R4: 10k
P1 (trimpot): ? (replaces 56k resistor; possibly 100k)
pep pot: 50? ???
volume pot: ???
q1: BC107
q2: BC107

9V battery
Any more infos/pictures/input anybody? Looks as if it might be closely related to the Tone Bender MKI.V/Fuzz Face.

Note that the red, wedge shaped "Fuzzy" pedal is a different circuit. Discuss it here: https://www.freestompboxes.org/viewtopic.ph ... it=pep+box

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Post by drewl »

I was going to mention The Beatles using one on Revolver era, but they have the pic of John w/one.

I always figured it was Tonebender MKI variant but have no idea really.

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Post by Electric Warrior »

right, that was the Fuzzy (see other thread) ;)
The Pepbox/Rush Pep Box is different.

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Post by controller700 »

https://stompboxes.co.uk/forum/viewtopic ... t=pep+fuzz

If it´s a cousin of the MKI than it´s not so interesting for me. Maybe someone can post a nice clip?? :mrgreen:

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Post by Electric Warrior »

It's NOT. The Fuzzy is well documented in the other thread and is a FZ-1A clone (i.e. a three transistor circuit very similar to an MKI), while the Pepbox/Rush Pep Box (the very unit THIS topic was supposed to be about) is a two transistor circuit and might be very similar to a Fuzz Face.

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Post by Electric Warrior »

alright, it's entirely possible to connect the parts in a Fuzz-Faceish manner.. note that this is pure speculation :wink:
circuit.jpg

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Post by Electric Warrior »

found some more data and detailed photos on the D*A*M forum: https://stompboxes.co.uk/forum/viewtopic ... t=rush+pep

New component list:
C1: 12.5µF electrolytic
C2: 12.5 µF electrolytic
C3: 0.01µF, styroflex
C4: ?, styroflex, larger physical size than C3
R1: 1M
R2: 1k5
R3: 100Ω
R4: 10k
P1 (trimpot): replaces 56k resistor; possibly 100k
pep pot: 10k log
volume pot: 50k log
q1: BC107 (or BC109C)
q2: BC107

9V battery

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Post by noelgrassy »

That Graham has all the cool shit! I wouldn't see half of this stuff were it not for your great site and
Graham's willingness to share some of his collection.

12.5µF is gonna be tough to find aren't they? I guess two 25µF in parallel will be fine in a pinch.
I see a BC109X the vertical line following the nine is tall enough to be the back of a letter B too.
Graham says it's a "C". Now to get him to measure the gains in the socketed xistors...

Thanks for starting this thread BTW,

NG.
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Post by Electric Warrior »

Yes, Graham's collection is quite amazing.

Looks like a C in the 10th photo.. His other Rush Pep has two BC107s.
If you consider the tolerances of old electrolytics, 10µF would be alright. There's even some 12µFs available: http://www.banzaimusic.com/Panasonic-FC-12uF-63V.html

I guess I confused the caps in the parts list.. I believe the 0.1µF one (Vishay replacement) might be the output cap. The parts are laid out a bit differently in that later unit..

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Post by Electric Warrior »

btw, what site of mine? :shock:

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Post by IvIark »

noelgrassy wrote:12.5µF is gonna be tough to find aren't they?
In the last batch of 10uF electrolytic caps I bought, there were quite a few that measured around 12.5uF. Sometimes crap caps come in handy. :)
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

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Post by Electric Warrior »

:D

can anybody come up with a nicer way to connect Q1? I don't think they would have put a trace to the right of R2. Kinda close to the edge.
I might have interchanged R1 and R2's positions in the circuit, but I can't find any better way to connect them..

From the other circuit board layout I gather that C3 is more likely connected to Q2's base and collector than to Q1's.

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Post by Dan N »

noelgrassy wrote:12.5µF is gonna be tough to find aren't they? I guess two 25µF in parallel will be fine in a pinch.
That would give you 50 uf. You'd want them in series, not parallel.
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Post by noelgrassy »

Electric Warrior wrote:btw, what site of mine? :shock:
I was confusing you with the fellow who maintains The Effects Database. DiscoFreq is his handle I believe.
I'm bad enough with names let alone aliases. :oops:


DanN, You are correct sir! I have a way of confusing the resistor formula with the capacitor formula. Though
I would've got it right after soldering everything up nice and neat. :roll:


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Post by Electric Warrior »

noelgrassy wrote:
Electric Warrior wrote:btw, what site of mine? :shock:
I was confusing you with the fellow who maintains The Effects Database. DiscoFreq is his handle I believe.
I'm bad enough with names let alone aliases. :oops:
I see :mrgreen:
A very useful site, indeed!

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Post by noelgrassy »

Electric Warrior wrote:here's a preliminary schematic:
WEM Rush Pep Box.png
Niceness! I believe I have the parts to hand actually and
I'll lash this together with two metal can BC108B this AM and see what it poots forth.
Thanks Electric Warrior!

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Post by drewl »

Hmmm....gotta' try this.
Low Beta transistors? Like around 100hfe?

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Post by Electric Warrior »

According to a 1969 ITT data sheet BC107As should be 125…260, BC107Bs 240…500 and BC109Cs 450…900
Niceness! I believe I have the parts to hand actually and
I'll lash this together with two metal can BC108B this AM and see what it poots forth.
Thanks Electric Warrior!
cool. I'm looking forward to your findings!

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Post by drewl »

Well I put one together at work and just tried it out.
I have a big metal box with pots and jacks etc. for trying out different effects, just tack in the leads and you're good to go.
I biased it to around 4.5v on Q2's collector, and that seems to be the sweet spot for it. nice vintage fuzz sound, the gain pot didn't look like it was doing much on a scope, but with a guitar it really has a wide sweep, a little bassy when turned down, but a good raspy fuzz when cranked.
I forgot to put the cap in between the transistors, I'll have to see what difference it makes when I install it.

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Post by Electric Warrior »

nice! I presume the cap between the transistors was put there to prevent oscillation.

There's a 5 printed onto one of them in the pictures. Could that possibly mean it's a 5pF cap? Seems rather small to me..

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