Fuzz Factory Failure.

[Milotic]

Hi guys

Just build a Fuzz Factory using this schematic
http://2.bp.blogspot.com/_y4AYtND8Hz8/TCINTn3D6JI/AAAAAAAAAY0/wBxmQy75fJ8/s1600/knownworkingtotal.gif

Followed the schematic pretty methodically.
However since i have no clue on how to obtain some AC128's, i used BC558's instead.
The problem i'm having is the pedal isn't fuzzing very well.  All im getting is a slighty fuzz that isn't really loud even with the volume fully cranked.
Took a voltage reading, realizing that the voltage is affected by the stab konb, so i turned all the knobs fully, so the collector reading on the transistor reads at around 9.5v (source voltage).

Q1 BCC558
C: 9.39v
B: 8.59v
E: 9.4v

Q2 BCC558
C: 8.11v
B: 8.96v
E: 9.55v

Q3: 2N3904
C: 9.3v
B: 0.64v
E: 0v

I'm not sure if the E readings are suppose to be higher than the C/B on the transistors, but according the the layouts it seems like its suppose to be like that.

Regards

[MikeH]

In my experience the type of transistors for this project is kind of important- I built one with a quality set of tested AC128s which worked beautifully, but I sold it to a friend.  I've since then tried to build one again, using Fuzz Face sets from small bear or ebay grab bag junk and all have had far too little gain to really be effective in this citcuit.

[mth5044]

Sorry, I'm not any help with your problem here, but I think we could both benefit by this question-

What are good replacement transistors for this circuit?

[Schappy]

Has anyone else had trouble with smallbears matched sets producing enough gain in a fuzz face?

[LucifersTrip]

Sorry, I'm not any help with your problem here, but I think we could both benefit by this question-

What are good replacement transistors for this circuit?

All I did was swap a bunch of random Ge's in and out till it sounded best. I wound up with Q2 = 65, Q3 = 96

http://www.diystompboxes.com/smfforum/index.php?topic=87177

good luck

[CynicalMan]

I don't think this is a transistor issue, or if it is, it's more major than having too low an hfe.

Do you have Q1 and Q2 the right way around? If you are using BC558, then you should have them the opposite way than they are shown in the layout. Their pinout is CBE.

[Milotic]

Hm i think Mr Cynicalman is right.  Forgot about that, PNP are reverse of NPN iirc.
And now the Fuzz works!  but doesn't squeal like the original FF.

[ultran8]

i found ac128 at mcm
http://www.mcmelectronics.com/product/AC128