GasPedals - Dumbbell  [traced]

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skibum1999
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Post by skibum1999 »

Does anyone have any info on this pedal. It's a 2 channel, 1 knob "dumble-in-a-box". Sounds very good.

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Post by marshmellow »

One knob should be sufficient for cutting treble I guess :lol: :roll:

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Post by Dr Tony Balls »

Anyone know whats going on in these?

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Greg
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Post by Greg »

Fully gooped on both sides..
it's a decent sounding OD.. but not really exciting or different enough that I'd spend the time it'll take to degoop right now.
:?

I had a little pick at one corner, but the epoxy is pretty solid and there'd be a good chance of trashing the board during a degoop and trace.
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Dr Tony Balls
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Post by Dr Tony Balls »

Thanks, greg.

I've heard clips and I agree that its nothing that exciting to me. However I sweet trading deal with a friend who wants one (I build him all the pedals he wants and he send me luthier gear and services in return). So i'd still like to make one if anyone has info about the circuit.

I cant imagine that it's too complicated. The size suggests that its pretty simple, plus all of his other stuff is really bare bones.

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Post by ppluis0 »

Hi there,

To dissolve the goop if it were made of polyester resin, the object can be dipped in trichlorethylene.

The board should be placed in a container that can be closed (to prevent evaporation of the solvent) and every two or three hours digging with a screwdriver, a knife or sharp objects that everyone likes to use.

This scale can tease out of resin. The additional problem is that this solvent breaks down the insulation of the wires and may damage some kind of plastic, so you have to take that into account since this procedure is quite bizarre.

Enjoy it !!
Jose

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Post by Saruman »

any news?

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Post by Greg »

Dr Tony Balls wrote:Thanks, greg.

I've heard clips and I agree that its nothing that exciting to me. However I sweet trading deal with a friend who wants one (I build him all the pedals he wants and he send me luthier gear and services in return). So i'd still like to make one if anyone has info about the circuit.

I cant imagine that it's too complicated. The size suggests that its pretty simple, plus all of his other stuff is really bare bones.
It's a decent sounding OD.. not terribly versatile though without any Tone control... for me it could be a little brighter.
He made a 2nd version with Tone control I think.
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Post by sonicmojo »

I'll resurrect this thread from the dead. Here is Dumbbell V2 with two switches and the VOL/TONE/GAIN knobs. I had a little fun with this one last year trying to ungoop it. The IC socket for the resistors is a very good idea for tweaking. Here are my suggestions if you decide to build this circuit. The top IC socket resistor (7.15k) is for tone sweep. Modify down, like to 2k for more tone sweep control. The second IC socket resistor (150k) is for gain. I modified this down to about 33k for more sweep and possibly a little less overall gain. This thing may squeal into an overdriven amp unless you adjust that stock resistor. The bottom two resistors on the IC socket are bypassed by the second footswitch for more overall gain. Tweak as desired. The pedal sounds great into a clean amp for sure. I've built five Dumble style amps and can get pretty darn close to the overdrive channel sound through the clean channel using this circuit.

It is a double sided PCB but hopefully you can see all the traces in the pics including the last one which is a composite of both sides. All values noted are the stock values as measured when I received the pedal. I never drew a schematic, please do if you want and send me one :D. Have fun!

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Blue Trace=front side
Yellow Trace=back side
Silver Trace=both sides
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Post by beedotman »

Awesome post and work! :applause:

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Post by Greg »

Why would he socket those resistors ??
:scratch:
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Post by sonicmojo »

Greg wrote:Why would he socket those resistors ??
:scratch:
I wouldn't do it unless I was experimenting. They can fall out too easily.

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Post by Cannibal »

Greg wrote:Why would he socket those resistors ??
:scratch:
Probably he just messed up, the socket was for the IC but he put it in the wrong place. :D
I'm gonna try to trace a schematic for this, it shouldn't be that hard.
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Post by Lucifer »

Hi SonicMojo,

Thanks for posting the pics - and for the patience to do the de-goop.

I've traced out the first stage so far - input with 1Meg to ground, through 47nF to IC1a pin 3, which also has 470k to Vb. Two Leds, back to back in the feedback loop, with 100pF in parallel as well as a 250k pot in series with 150k resistor. Pin 2 of the IC also goes through 22nF and 2k to Vb. All pretty straight forward.

The output of the first stage goes via 7k15 and 10k pot (pins 1 and 3) to IC1b pin 5, also with a 10nF shunt from pin 5 to ground. There's a 1k feedback resistor around this stage, and its output goes through a 10uF cap to the 500k output pot.

The right hand switch wiring that you've drawn is supposed to be a normal 3-pole bypass switch, but some of your drawn wires go to the wrong places. That's OK, and easily decipherable. What's throwing me is the left-hand switch, which I assume is some sort of boost, but I can't be sure of the wires that you've drawn, so I'm not sure how it works.

Would you please be so kind as to check (and possibly re-draw) the wiring to the switches.

Sincerest thanks :twisted:
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Post by sonicmojo »

Lucifer,

I have made an exact clone and I just double-checked all the wiring to the switches as well as the drawing. I am sure it works as drawn but I'm sure there is more than one way to skin the cat on the wiring. The left hand switch when looking at the upside down layout basically bypasses just the two bottom resistors on the IC socket as far as I had figured out way back. The way this unit works is that the left switch (looking from the top) turns it on and off. The right switch (from the top) is the "resistor removal boost". If the left on/off switch (looking from the top) is not engaged, the right switch does nothing for the sound but does, in fact, light the LED. I hope I didn't confuse the issue. This is just how the unit works.

Here is my original hand drawn version if you want to double-check:

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Post by Lucifer »

Thanks for the reassurance, SonicMojo.

However, if you look at the right hand switch (the bypass switch) in your last picture, the top left wire and the one below it are reversed - the input jack should connect to the middle terminal, otherwise (as drawn) you'll short circuit the input to output rather than bypassing the circuit - well, you would if the output side of the switch was drawn correctly . . .

. . . The output from the 500k pot gets switched to the LED, instead of to the output jack, according to what you've drawn. The LED should be connected to ground when not in bypass mode.

It's because of these errors that I don't know if your left-hand switch wiring also has wrong connections.

I'm not trying to knock what you've done - I applaud your efforts - but the connections are incorrect, and I just want to get them sorted.

Anyone else care to chime in ?
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Post by sonicmojo »

The output from the 500k pot does not switch to the LED. That side of the LED is connected to ground only, through the switch via the back side of the board (yellow trace). It is a double sided board. If you look at the color codes I provided, you will see that it does not short. Just because it is silver on the composite, it does not mean that it is connected on both sides. The silver traces follow the same path on both sides of the board but are not necessarily connected, except at the holes in general. It is confusing being a double-sided board.
Last edited by sonicmojo on 24 Oct 2012, 13:23, edited 1 time in total.

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Post by Lucifer »

You're right, SonicMojo, and I apologise.

The tracks are very confusing, but I can see sense in the switch layout now - it's an unusual layout, but it does make sense.

Sorry for doubting you. :oops:
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Post by sonicmojo »

No worries. If you come up with a first pass, I can verify. :D

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Post by Dr Tony Balls »

Here's my drawing from the first set of pics. Totally unverified....just drawing out what I see.

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