Problems with Fuzz Face Build

[vanessa]

I just got finished with a Fuzz Face build that I built for a friend of mine. It's an Axis Fuzz silicon off the fuzz central site.

The problem I get is when the volume control on my guitar is completely off and the amp and pedal is still on I hear the radio coming through my amp. Not overpowering but faintly in the background. As soon as I turn up the volume control on the guitar just enough to hear the guitar it goes away.

I tried using two different amps and two different guitars and the same thing. I've built this one before and have not had this issue. I went through the circuit and can not find anything out of the ordinary. I tried with a battery and with the AC jack and the same thing. I don't get any radio interference when the pedal is unplugged. Is this normal?



:roll:

[H.Manback]

Not really, sounds like a grounding problem. Check if that is all correctly wired. Then double check.

[vanessa]

I have double checked the grounding. Nothing to be seen. I thought maybe a ground loop but I disconnected what I thought it would be and the circuit was almost dead as a result. I hooked it back up and it works great, just the radio noise when the volume control of the guitar is shut off.

:roll:

[spudulike]

Try a small value cap - eg 47pF - between input and gnd for rf rejection.

[brian wenz]

Hello Hello Vanessa--
      What transisors did you use???  I've been messing with 2n2369 for Fuzz Faces and I'm having exactly the same problem.  When I put another higher-gain tranny in Q1 the  radio stations [and some hiss as well...] go away!   Somebody reminded me that the FF circuit  biases better with higher gain trannys so I put a 150 ohm resistor betwen Q1 's emitter and ground and it helped quite a bit.
Brian.

[vanessa]

Hello Hello Vanessa--
      What transisors did you use???  I've been messing with 2n2369 for Fuzz Faces and I'm having exactly the same problem.  When I put another higher-gain tranny in Q1 the  radio stations [and some hiss as well...] go away!   Somebody reminded me that the FF circuit  biases better with higher gain trannys so I put a 150 ohm resistor betwen Q1 's emitter and ground and it helped quite a bit.
Brian.

Brian, I love all your input on this forum. I've learned so much from your suggestions. Thank you.

Yes in Q1 I'm using the 2N2369A. But I came up with a solution already. I thought the external bias pot was kind of useless on this circuit. I figure once you have found the 'clean' that you like you would just set it to it and want to leave it. Why spend the extra cash eh?

The first Axis I built had the pot in it and worked great. This one I decided to leave it off in favor of a resistor value I like.

So I found that I like an 8.2k to a 10k resistor in series with the circuit after the input. When I ran this post I had that resistor out of the board. As I was testing some other issue that I was having at that time.

After putting in the resistor all those issues went away. I wonder why? I'm no EE. But I have to ask the question. With the 2N2369A why would you need to put a resistor in series before the circuit to make it work?

[brian wenz]

Hello Hello--
    So you put a fixed resistor [instead of the 100K "smooth" pot] at the front of the circuit?   That would be like turning down the pot just a little bit and leaving it.  I guess it just takes  enough of the signal down to cut out the  radio station racket.   I've found that sometimes a fixed resistor at the front of a circuit can ADD noise, too!   I've talked to other people about this problem I've had with the 2N2369 and they said they haven't had any problems at all!   This kind of crap drives me nuts 'cuz I don't know enough about electronics to nail the problem.
Thanks for the compliment ......all I can do is relate experience that I've had!
What kind of guitar and amp are you using??
Brian.

[petemoore]

resistance before the input makes input look more like a current source, increasing the linearness of the gain...so I've heard...and it seems to bear out in function.
 I don't have pickups the FF was 'designed' for, so rolling off the guitar vol, or using input gain mod seems more necessary to me than have the traditional gain control...I preset the 'gain' where I like it [1k+] or use an internal trimmer, substituting the gainpot with an input gainpot.

[vanessa]

Hello Hello--
    So you put a fixed resistor [instead of the 100K "smooth" pot] at the front of the circuit?   That would be like turning down the pot just a little bit and leaving it.  I guess it just takes  enough of the signal down to cut out the  radio station racket.

Yes and it cleans it up the circuit a bit as well.

What kind of guitar and amp are you using??

I was using a old Dano 'Pager', and a Tele. Amps, JCM 800 and a Ampeg VT-22.

At first I thought maybe it was the guitars and amps but it seems it just might be something with that 2N2369. Could it be biasing with this circuit?

[brian wenz]

Hello Helloooooo-
    Something I noticed was that when I tried a guitar with humbuckers the problem got ALOT better........maybe the single coil Fender pickups  are part of the problem.  [Well, actually they would be part of the problem because single coils are noisier anyway....!]  I wonder if Phillip at Fuzz Central has noticed this with his pedals???  
I think the fact that these are low-gain trannys makes them problematic in the Fuzz Face circuit [like I mentioned earlier...].   All I know so far is that adding that 150 ohm resistor on Q1's emitter helped.
Brian.
WWW.OTTOSGUITARS.COM

[Eb7+9]

I built one of these a while back from the FC schem and had similar problems ... two things I found to help :

(i) the 220 and .001uF values in RED should read 220k and 0.001uF I think ... this produces a high freq. shelving aimed at curbing RF from leaking in ... makes most sense and works ...

(ii) keep your wiring short and tidy ... avoid too much wiring crossing/proximity with this circuit ...

~jc

[vanessa]

I built one of these a while back from the FC schem and had similar problems ... two things I found to help :

(i) the 220 and .001uF values in RED should read 220k and 0.001uF I think ... this produces a high freq. shelving aimed at curbing RF from leaking in ... makes most sense and works ...

(ii) keep your wiring short and tidy ... avoid too much wiring crossing/proximity with this circuit ...

~jc

Are you talking about the Axis Fuzz Face Rev.3

:roll:

[mac]

I built one of these a while back from the FC schem and had similar problems ... two things I found to help :

(i) the 220 and .001uF values in RED should read 220k and 0.001uF I think ... this produces a high freq. shelving aimed at curbing RF from leaking in ... makes most sense and works ...

(ii) keep your wiring short and tidy ... avoid too much wiring crossing/proximity with this circuit ...

~jc

Are you talking about the Axis Fuzz Face Rev.3

:roll:

Hello Vane....

Silicon versions of the FF are cool fuzzes, but are also very nice radios  :lol:
The problem is that you can build a circuit that does not pick up RF, then unsolder & rebuild it with the same parts and ... what??? RF interference!!!
The problem is that sometimes a bad soldering, leads too close, or long leads introduce some extra capacitance and inductance that resonates with a radio station frequency. Also the distance between parts and the case may cause interference.
I had that problem with my MXR+. I bended some caps and resistors leads 90º  until I found the one that was picking up RF.
Try this before everything else. Move some parts' leads and try to avoid open loops especially with caps.
Sometimes it is helpful to introduce a small screwdriver below caps,  resistors or open loops, and hear if it increases RF noise.

If this does not help try a cap of about 47 - 220 pF from both transistors' collector to base.

As for the 2N2369A I used a MPSA42 or a lower gain BDXXX (131,139,237) instead. I got some extra 'mojo' when using medium to high power low gain transistors. The Ge versions use that kind of transistors. Anyway I think that the 2369 are a good choice.

See my post at fuzzcentral.tripod.com about the Si & Ge FF and visit my site at geocities.com/guitarfxs/

Good luck  :wink:

mac

[Julle]

I got the same nice thing with my Hornet Fuzz Face... And a Ibanez Amp.... I turned the Gain totaly i up on the amp and up on the pedal and turned the vulume down on my guitar..... And i have a radio..... Wired but fun :lol: