Big huuuum sound on a fuzz face

[melkaone]

Hi all
Ok, I know, this really is a simple build
But when i turn it on, i've got a huge humm sound (noise). The humm respond to the volume et fuzz pots, and the effect works, when i play a note, i hear the distorted sound (still with the noise). I worked with the schematic from GGG, with PNP AC128 (hFE 16 and 18 for Q1 and Q2) transistors and negative ground, and i changed the 22uF cap by a 47uF (effect for a bass). The effects isn't yet boxed. And i made it on a perfboard.
I have been checking the circuit for 2 hours now, and i still do not see any shortcuts or routing error.
Ideas?

[petemoore]

I didn't read the post.
 Connect to ground the black lead, set DMM beep Mode, test all grounds shown on schem.

[Hal]

i read the post

put it in a box

[melkaone]

ok, i'll do it as soon as i have changed my fuzz pot, i burned it trying to solder something without deconnecting the power jack!
and, well, i also destroyed my tiny aluminum box (never try to make a hole in metal with what you use with concrete )
i'm really stupid

[phillip]

Definitely put it in a box...the grounded metal box helps shield the circuit from outside sources of nose such as TV and comptuer monitors, flourescent lights, etc.

I would also say to wire it up as PNP positive ground and don't use the PNP negative ground arrangement...this has caused problems before, and if it's your first pedal, it could cause some unnecessary headaches.

Phillip

[David]

ok, i'll do it as soon as i have changed my fuzz pot, i burned it trying to solder something without deconnecting the power jack!
and, well, i also destroyed my tiny aluminum box (never try to make a hole in metal with what you use with concrete )
i'm really stupid

You mean you used a hammer drill, or a masonry bit?
You're not stupid, you just believe in killing a fly with an atom bomb!
Use a "Vari-Bit" or "Unibit" if they're available in your part of the world.  The generic name is "stepped drill bit".

[george]

also check that you have wired up the jacks correctly - ground to collar, hot to tip

[petemoore]

I don't like thinking about jacks and switches when debugging a circuit.
 I find it's easier to fractionalize the work, doing one 'section at a time, wherever possible.
 PNP Transistors work with Pos Gnd.
 The number of u's in 'hum' tracked my thinking that it's caused by something else, just not being in a box usually means a little more noise, but usually not serious hum {YMMV].

[Fret Wire]

I worked with the schematic from GGG, with PNP AC128 (hFE 16 and 18 for Q1 and Q2) transistors and negative ground, and i changed the 22uF cap by a 47uF (effect for a bass).

Is that a typo, or are Q1 16 hfe and Q2 18 hfe? Pretty low, gain wise. Was the leakage measured? If so, what was it? If it bias' up, it could still make an effect, I suppose. For low gain Ge's, I found that using them in a Tonebender ckt (with some adjusting) will still make a decent fuzz.

[petemoore]

Low gain transistors would not necessarily induce hum.
 How was the gain checked?
 The leaky ones I have are hissy, but not hummy.
 Check out GEO, Technology of the Fuzz Face. There is reference in that article as to transistor gains and Fuzz Face performance.

[Fret Wire]

I wasn't addressing the hum, the other posts covered that. I'm just curious about the gain on those. I've fudged the "magic range" on both ends but never that low.

[petemoore]

I have 'old 'ge's around, built a series of Rangemasters [2 added on 1 board to the boxed one] for the ones that didn't make the FF cut.
 Heavy FF type tones, other interesting tones too, trimpots for biases, Rangemaster knobs, caps and Q's. No FF guitar volume gain rolloff.
 Socketting transistors on a FF and swapping, and/or getting a matched pair from Small Bear, one can find Great FF performances.
 I test Pos Gnd FF Boards Intended for Ge's with 2n3906's or other PNP Q's, when It 'sparks, I then try the prized ge's.

[petemoore]

ok, i'll do it as soon as i have changed my fuzz pot, i burned it trying to solder something without deconnecting the power jack!
and, well, i also destroyed my tiny aluminum box (never try to make a hole in metal with what you use with concrete )
i'm really stupid

For testing, to see if the PS is causeing hum, try a PNP Pos Gnd. FF, 'just invert + and - on the polarized capacitor[s?] and the battery clip, and use a battery. My FF's huuum when a Wall Wart is tried.

[petemoore]

After messing with a circuit, I often check for a shorted PS connection between battery clip - and + using the DMM continuity checker.

[george]

I don't like thinking about jacks and switches when debugging a circuit.

I didn't read anywhere that melkaone HADN'T soldered up the jacks yet ....?

and who said anything about switches.

believe me get your jacks wired up the wrong way and the hum will be louder than your guitar signal ....

and it's a pretty damn simple check - do that first then "fractionalise" to your hearts content IMO

[Brian Marshall]

power supply noise.... if you are using a negative ground, but using pnp trannys, and using the + side as sort of a reference voltage (well not really but i think you might understand what i mean) then i'd look at the power supply... if you are using a battery, then see the posts above

[melkaone]

well, it's gonna be hard to answer all of you!

phillip > well, i was testing it on my desk, with my 17" CRT monitor on... maybe that's a source of pb
i'll check the PNP positive ground version, if anything else doesn't solve it

david > well, i made a first small holle with a metal bit (don't know the english word) and i tried to make it bigger with a masonry bit. didn't work. i gave the box to my brother, he'll do it at his job, he have all that is needed, even the skills ^^

george > double checked, it's good, thx

petemoore > well, i wired as less things as possible, i did't put the switch, and i fisrt connected the jacks to see if the signal was going through my circuit.
i'll try the pos grnd version.

fret wire > I bought 5 AC128, and those two were the ones with the highest hfe... I don't even know what that means, but i heard that i had to put the highest i could find on the circuit.

petemoore > i tested it with a DMM with a transistor checking range. but this is a cheap one.
and thanks for the advices about the pos grnd version . I just pluged a wallwart, but i'll try with a battery clip

so, wednesday, when my electronic shop opens, i'll take a brand new box, drill it carefully (i'll let my brother do it, why should I bother?), put the circuit in it with a battery clip, and try the whole thing far away from my computer. If that doesn't work, i'll try the positive ground version, and if that still doesnt work, i'll at least have a great noise generator, can be useful in experimental music.

thanks to you all, guys (and girls, maybe, don't know)

[petemoore]

well, it's gonna be hard to answer all of you!

phillip > well, i was testing it on my desk, with my 17" CRT monitor on... maybe that's a source of pb  {YES}.
i'll check the PNP positive ground version, if anything else doesn't solve it
 {EZ...I would suggest it's worth it to see}
david > well, i made a first small holle with a metal bit (don't know the english word) and i tried to make it bigger with a masonry bit. didn't work. i gave the box to my brother, he'll do it at his job, he have all that is needed, even the skills ^^

george > double checked, it's good, thx

petemoore > well, i wired as less things as possible, i did't put the switch, and i fisrt connected the jacks to see if the signal was going through my circuit.
i'll try the pos grnd version.

fret wire > I bought 5 AC128, and those two were the ones with the highest hfe... I don't even know what that means, but i heard that i had to put the highest i could find on the circuit.
 70hfe - 130hfe [ballpark] higher ones will work, but differently.
 Use the lower Hfe gain of the two for Q1.

petemoore > i tested it with a DMM with a transistor checking range. but this is a cheap one.
 >>>this test for 'where'd they come from Ge's is ...uh... inaccurate for FF Q picks.
and thanks for the advices about the pos grnd version . I just pluged a wallwart, but i'll try with a battery clip
 >>>I'd say worth tryin a battery, that way you can isolate, and tell how much noise the PS adds.

so, wednesday, when my electronic shop opens, i'll take a brand new box, drill it carefully (i'll let my brother do it, why should I bother?), put the circuit in it with a battery clip, and try the whole thing far away from my computer. If that doesn't work, i'll try the positive ground version, and if that still doesnt work, i'll at least have a great noise generator, can be useful in experimental music.
  >>>Just turning the monitor off should do it, compare with computer on/off if further noise isolation is desired.
thanks to you all, guys (and girls, maybe, don't know)

>>>Careful with that iron around the GE's, use heat sinks if you need them.

[melkaone]

what do you think about the possibility of the noise coming from the bass?
Well, i have a passive 4 strings aria pro II, and i heard that passive electronics can "capture" (i should check my dictionnary sometimes) all the interferences around (like my monitor).

well, hum, no, forget what i just said cause when the FF is turned off, i have no noise....

[petemoore]

One way to tell if that's not what's causing the hum is disconnect the source [guitar] from the input jack and see if the hum continues.