GM Fuzz Up FD-3B

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

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Thought you all might enjoy this one.
The slightly earlier version of this pedal is essentially a 9v germanium FZ-1 with controls to boost the highs or lows. This version has three 2N 5172 transistors and works in the same way, but sounds quite a bit more aggressive. Not sure if this circuit is reminiscent of anything else?
The FD-3A version seems to have been made in 1967 and 1968, and this version from what I can gather came later that same year. But tbh, I don't know anything for certain.
Last edited by edkoppel on 20 Jul 2022, 09:10, edited 2 times in total.
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soggybag
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Post by soggybag »

Great stuff! The “high fuzz” and “low fuzz” is intriguing. Is there a schematic?

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EmmG
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Post by EmmG »

It looks like the "FD3-B Dual Range"
https://www.effectsdatabase.com/model/g ... nics/fd3/b (same unit as this one)
https://www.effectsdatabase.com/model/gmelectronics

There's also the potentiometer board:
High #1, Low #1, Intensity #2&3 are connected.

Image

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edkoppel
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Post by edkoppel »

Yes, this is the same exact unit that's on effects database. I accidentally typed an M instead of D. 🤙
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BMS1971
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Post by BMS1971 »

interesting, any idea of schematic?

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Lani
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Post by Lani »

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Do these look like bad joints, or am I going blind. The top one which is the base of the middle 5172 (I think) looks like it's not even connected. The one below that looks dry. Does this unit work?

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Manfred
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Post by Manfred »

I started this layout clone, next I will trace the circuit structure.
the dimension of the board is 3" by 3"
GM Fuzz Layout.jpg

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Post by edkoppel »

Manfred wrote: 14 Aug 2022, 08:29 I started this layout clone, next I will trace the circuit structure.
the dimension of the board is 3" by 3"
GM Fuzz Layout.jpg
Nice! Let me know how it sounds once you get it wired up. 🙏
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Post by Manfred »

There I will have to disappoint you, I make the layout clone only first to find the circuit structure and then it is freely available to all.
Also the capacitor values are not to be recognized, there remains only to hope that an owner of this fuzz reads the for us.
How it sounds you can listen here:


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Post by CheapPedalCollector »

The red one sounds a lot better, the 2nd one sounds broken to me.

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Post by cspar »

They both seem broken to me.

The intensity pot doesn't seem to work in the red one's demo. At least it sounds better though.

The wiring is a little unclear to me from the pictures and from the solder side of the potentiometer board it looks like there might be a few more components.

Maybe there's capacitors tucked under the tone pots on the enclosure topside facing part of the board?

It's hard for me to tell from the pictures what's really going on with all that.

Do you still have the pedal edkoppal?
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Post by nightraven »

Here are a couple of gutshots of another black Fuzz Up like Ed's. I hope the owner of this pedal won't mind me sharing the pics!

Image
Image
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Post by cspar »

It not being yours I can totally understand not wanting to take it apart but can you verify if there are any components on the board with the potentiometers? Even if you can't get a good picture of them.

From how many solder spots there are on the back side it seems that there are some there.
"Just because the forgoing circuits have produced results there is no reason experimenting won't lead to added results." L. E. Darling, in his article containing the earliest published vacuum tube synthesizer circuit, Popular Science Jan 1920

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Post by Manfred »

cspar wrote: 16 Aug 2022, 16:32 It not being yours I can totally understand not wanting to take it apart but can you verify if there are any components on the board with the potentiometers? Even if you can't get a good picture of them.

From how many solder spots there are on the back side it seems that there are some there.
I agree with you.

@nightraven
can you at least give us the sources and destinations of the wires between the potentiometer board and the jacks and measure the values of the potentiometers with an ohmmeter?

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Post by edkoppel »

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Sorry to leave you guys hanging!
Here is the component side of the board for the pots.

The video demo is of this exact unit but i can guarantee it sounds much better than that in person 😂 that was recorded in 2013 or so by the original owner on his even older phone, and sounds like it.

It does sound different to Jerms' which is the red one. And I'm guessing mostly because this is silicon and that's germanium.
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Post by edkoppel »

nightraven wrote: 16 Aug 2022, 14:08 Here are a couple of gutshots of another black Fuzz Up like Ed's. I hope the owner of this pedal won't mind me sharing the pics!

Image
Image
Whoa! This one is black inside too! Mine was clearly the early enclosure just painted black because the inside is red. 😂
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Post by Manfred »

Thanks for all!
Can you paste the wire colors of the incoming wires at the solder points in the yellow highlighted area?
Could you measure the potentiometer values?
The main board dimension of 3 "x 3" is an estimate of mine, are these dimensions correct, what are the dimensions of the potentiometer board?
Is it possible to read the missing values and types?
gm fuzz pcb top.jpg

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Post by edkoppel »

Manfred wrote: Today, 10:32 Thanks for all!
Can you paste the wire colors of the incoming wires at the solder points in the yellow highlighted area?
Could you measure the potentiometer values?
The main board dimension of 3 "x 3" is an estimate of mine, are these dimensions correct, what are the dimensions of the potentiometer board?
Is it possible to read the missing values and types?
gm fuzz pcb top.jpg
While i do appreciate the time you're taking to draw up a schematic, that inevitably the entire community can benefit from, i don't really want to open up this pedal any more than i already have as it's pretty delicate.

Simply being a collector and not a builder myself I in no way benefit from posting here, but choose to do so because I generally think it's much cooler to contribute to our nerdy pedal community than it is to hoard information away.

And in this case, I feel like there's more than enough to go off of here with the photos provided to get something cool enough to build from, even if that isn't an exact 1-to-1 clone
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