hi all, the guys at hcfx said i should try posting here...

i'm trying to build one of these:



from http://www.geocities.com/j4_student/schematics.htm

QuoteRoger Mayer Axis Fuzz - a fuzz that was designed to use readily available 2N3904 and 2N3906 silicon transistors. (ERRORS! (according to Joe Campagna, the following should be changed:
1) a 100k resistor needs to go from the base of the 2N3904 to ground.
2) the 2.2uf cap that feeds the volume wiper should have its negative side toward the pot.
3) the input caps should read .1uf (104k) & 470pf(471) 4) The cap from the drive wiper to ground should be 0.1uf not 1uf.)

and here is my attempt (big pic!).

those wires going off the bottom go to ground

im sure i'm doing something stupid. i'm not getting any sort of sound, i think my main problem is with working out how to wire up the ground / power and the two audio connectors.

i have some of these these and these

i've put some resistors in place of the pots (less than the specified value)

any help would be amazing

Welcome home.

If this is your first such build, there are several things that may be likely sources of nonfunctionality.

1) Pinouts:  You'd think that with only 3 pins it would be hard to misidentify the pins on a transistor, but no.  Between the different possible substitutes for specific part numbers (e.g., bubble packs billing themselves as 2N3904 which have similar specs but a different pinout) and the often ambiguous drawings on datasheets (Is that looking "down" from the flat top of the device, or looking "up" from the ends of the pins?), it's a wonder anyone gets it right first time around.

2) Orientation: Cap polarity makes a difference.  Make sure all the +'s go where they should and the -'s too.

3) Jack solder terminals:  With the exception of the painfully obvious, like those "Marshall-style" plastic jacks where you can see the contacts lying over exactly where they will touch the plugs, it can be easy to mistake one lug for another on a closed circuit or sterewo phone jack.  Tppo many of us here (myself among them) have *thought* we hooked everything up properly only to find that our input or output lead was actually going to the contact that was disabled upon plug insertion, or that our battery was NOT disabled by plug removal (and the reason why it doesn't work today is because the fresh alkaline you put in last night is now drained).

On top of this, note that there are plenty of older schematic draws posted around that, while someone may have eventually corrected them on a forum or other drawing, the original you downloaded was never corrected or taken down.

Quote from: Mark HammerWelcome home.

why thank you  . i'm going over those points right now although i'm not sure how to work out the way the transisters go around, there are no markings on them  :?.

i'm quite sure i've got my grounding sorted now tho  thanks to the wonderful faq.

any close up pics or any other detailed info required i'll be happy to oblige

Welcome  There are some different schematics floating around. Some have components for the Euro version that don't work here. Phillips schematic appears correct.
http://bryant02.home.att.net/schematics/axisfuzzschem.gif

Here's some old threads on the topic.
http://diystompboxes.com/sboxforum/viewtopic.php?t=20564&start=0

http://diystompboxes.com/sboxforum/viewtopic.php?t=20907

http://diystompboxes.com/sboxforum/viewtopic.php?t=20916

http://diystompboxes.com/sboxforum/viewtopic.php?t=18554&postdays=0&postorder=asc&start=0&sid=9d985eda68d674fe7ffe03c3e6d0ce7a

i thought i should just post this before i go to bed

image

i really can't see why this isn't working, i'm not getting any sound what-so-ever. could the jack wiring be wrong?

i dunno  :roll:

Quotei'm not sure how to work out the way the transisters go around, there are no markings on them

start your collection of datasheets with the 2N3906 and 3904!

Use google to search for "2n3906.pdf" or "2n3906 datasheet" etc.

My collection of transistors and op amps and etc etc is currently at 367 files and growing.

did you solder the jacks??

well it's alive! but it sounds less than great. i'm guessing thats down to the poor quality of the transistors.

i finally got some sound by adding a pot for the volume instead of just having nothing.

the volume works but the 'drive' doesn't do a whole lot.

thanks for the help people.

i must look into making one with better quality parts now...

Whoops, looks like the 2N3906 is shown backwards in the schematic. The emitter should point upward. I don't think the quality of parts should matter much, either.

-Joe

well i did manage to get it to sound a lot better, i had a 2K2 resistor where there should have been a 220R one. the drive control now works. it also boosts like crazy, i have to have the volume pot almost all the way down to produce the same amplitude, is this normal?

joe - changing round the 2N3906 doesn't do an awful lot, although it does change the character to a more broken sound, i've got it round the way it is in the schem, it seems to be more predictable that way.

I was wrong, misinterpreted the circuit. Most transistor circuits need the biasing tweaked to work right, might try fiddling with some values. I think where the 10k/22k resistors meet at the top should be somewhere between 4-5 volts, so that might be a good place to start. I made this on the breadboard once but can't remember whether I got it working or not.

-Joe