I built this mod of a fuzz face (see image for schematic) that allows you to switch between Ge and Si transistors. For Ge I used AC 176s, for Si I used a 2N4123 fr Q1 and BC108 for Q2. I bread boarded each circuit and it worked. Then I built the circuit in the picture, it still works, but the 500k volume goes from 0 to 50% and then back to 0. It does not go from 0 to 100%. It does it with both 500ka and 500kb pots. When I remove the ground, though, the pot increases from 0 to 100%.
(https://i.postimg.cc/G9pK8Qq3/modfuzzfaceschematic.jpg) (https://postimg.cc/G9pK8Qq3)
(https://i.postimg.cc/Yjy31Ws6/modfuzzfacepic.jpg) (https://postimg.cc/Yjy31Ws6)
Hi & Welcome.. :icon_wink:
By lifting Volume lug 1 up (removed grom GND) you effectively turn it into a rheostat (variable resistor) so the pot resistance is considered as upper part of voltage divider formed by pot and next effect input impedance..
So, what is that impedance..??
So you are suggesting I connect lug 1 to lug 2 to create a rheostat? How would I then measure impedance? Thanks!!
To what exactly you connect your build..??
It's connected to a Boss PSA-120S power supply, 9V, 0.5A, 4.5W output.
Sorry if that's not what you are asking for. I am new to this and trying to figure it out. Did a few kit builds, this is my first pedal from scratch.
Thanks!!
Can you share the complete circuit? Where does "switch pin 9" go? Transistor switch 1/2 X/Y? The lower "C"?
I don't have the exact schematic for the circuit. It's based off of this Fuller modification of the Fuzzface. This is also the stripboard layout that I came up with and used in the pedal. The E, B, and C's going to the emitter, base, and collector of the two red "transistor switches" that are 3PDT switches (shown in first post and in this first picture). This allows you to switch back and forth between the Si and Ge transistors. X refers to wires coming off of the collectors of the Si transistors, Y refers to the wires coming off of the collectors of the Ge transistors. 1 is Q1 and 2 is Q2.
Thanks for helping out with this! It's driving me crazy!
(https://i.postimg.cc/QHZV6vbx/fuller-schematic-and-transistor.jpg) (https://postimg.cc/QHZV6vbx)
(https://i.postimg.cc/w3CRC16z/stripboard-circuit.jpg) (https://postimg.cc/w3CRC16z)
Quote from: guywonder44 on April 10, 2022, 07:14:10 PM
It's connected to a Boss PSA-120S power supply, 9V, 0.5A, 4.5W output.
Sorry if that's not what you are asking for.
No need for sorry.. :icon_wink:
What I was asking is to what effect (pre-amp, power amp, delay, echo, e.t.c.) is your build connected..??
(what comes after Fuzzface till speaker(s)..)
I struggle with that stripboard layout. There are track cuts we can't see? The order of the 470R and 0.01uF output cap seems wrong - a trim pot should go in between, and where does Q2 collector go?
Quote from: antonis on April 11, 2022, 06:09:18 AM
Quote from: guywonder44 on April 10, 2022, 07:14:10 PM
It's connected to a Boss PSA-120S power supply, 9V, 0.5A, 4.5W output.
Sorry if that's not what you are asking for.
No need for sorry.. :icon_wink:
What I was asking is to what effect (pre-amp, power amp, delay, echo, e.t.c.) is your build connected..??
(what comes after Fuzzface till speaker(s)..)
Ahh, ok. It's just the fuzzface. I run a 2010 Fender Jazzmaster straight into the fuzzface that then goes into a 1970s Fender Twin.
Quote from: anotherjim on April 11, 2022, 07:30:32 AM
I struggle with that stripboard layout. There are track cuts we can't see? The order of the 470R and 0.01uF output cap seems wrong - a trim pot should go in between, and where does Q2 collector go?
I used the stripboard essentially as a breadboard. There are only two track cuts, which I labelled as drilloutbreak. The whole circuit is based off of https://guitar.com/guides/diy-workshop/diy-workshop-build-your-own-fuzz-pedal/. I just replaced the top 2 trim pots with 33k's and used a 10k and a 20k trim pot becuase I was getting such different gains off of the transistors.
The Q2 collector from the transistor switch probably doesn't need to go to strip 7, but the collectors of the Q2 Si and Ge go to the 10 and 14 strip, respectively.
I'll double check the 470R and the 0.01uF to make sure that's correct. I just don't get what would cause a pot to go from linear or log to increasing and then decreasing (parabolic?). It's like the two resistors in the pot are not working together but independently if that makes sense.
What is Switch pin 9 (on your first schematic..??)
I assume switch 9 is a 3PDT footswitch.
Pot action going up>down>up suggests the wiper lug 2 goes to 0v instead of output and both lugs 1 & 3 carry signal!
Yes, switch pin 9 is the pin on the 3PDT foot switch.
Anotherjim - what would make the wiper lug 2 go to 0v instead of output and both lugs 1 & 3 carry signal? When I remove the ground, it doesn't do this and increase linearly. I tried to use the pedal with the ground removed from the volume pot, but then the volume never goes to 0.
Quote from: guywonder44 on April 11, 2022, 09:29:31 AM
There are only two track cuts, which I labelled as drilloutbreak.
That's a big problem. As drawn in your diagram, you will need cuts beneath the 100k and 470 resistors, and the two capacitors on the board.
Quote from: GGBB on April 11, 2022, 05:35:02 PM
Quote from: guywonder44 on April 11, 2022, 09:29:31 AM
There are only two track cuts, which I labelled as drilloutbreak.
That's a big problem. As drawn in your diagram, you will need cuts beneath the 100k and 470 resistors, and the two capacitors on the board.
I am not sure where the cuts should be you are referring to. Wouldn't that break the circuit?
I think I figured out why my volume pots are not working as linear or audio taper, but what i refer to as a "hill" taper, where the volume increases from 0 to 50 at 50% and then back to 0 at 100%. I can measure voltage across the three lugs of the pot. There is no voltage across the lugs of the volume pot in my breadboard version that works correctly. Thoughts?
This is where I got the design: https://guitar.com/guides/diy-workshop/diy-workshop-build-your-own-fuzz-pedal/
If you scroll to the bottom, you can see the schematics for a basic fuzz face (which I breadboarded and works correctly) and for a tweaked fuzz face (which I built on my stripboard). It works, so I don't think there are any incorrect connections. Where is this voltage coming from?
ya sure the pot ain't hosed? measure it across pins 1 and 3, and also check from wiper to each outer terminal. only time i ever found a pot acting like that, the wiper was smoked internally from dc. the pot still read proper value etc, until ya got to the dead spots in it. did that... turn it up half way, boom, turn it up past that and it ramps back down.
Yeah, I checked that and the pot is still good. I have even tested it out on 3 different pots, two linear, one audio, and they all do it.
Rich
Quote from: guywonder44 on April 12, 2022, 08:53:03 PM
Quote from: GGBB on April 11, 2022, 05:35:02 PM
Quote from: guywonder44 on April 11, 2022, 09:29:31 AM
There are only two track cuts, which I labelled as drilloutbreak.
That's a big problem. As drawn in your diagram, you will need cuts beneath the 100k and 470 resistors, and the two capacitors on the board.
I am not sure where the cuts should be you are referring to. Wouldn't that break the circuit?
Green circles:
(https://i.postimg.cc/YGNQNLMW/image.png) (https://postimg.cc/YGNQNLMW)
Without those cuts, both leads of the components are connected to the same strip, making them shorted to each other.
Yeah, that was it. Thanks, GGBB!! That's where the voltage was coming from. Once I cut beneath the capacitors and the resistors, the volume pot worked correctly and the pedal sounds great! THANKS!!