Vox Tonebender Biasing problems

[mellowyellow]

Hi,
I´m kind of new to this DIY-stuff, and as a matter of fact, this is my first new "thread" ever.

Anyway. I found the schematics for a Vox Tonebender, and it didn´t look that hard to build. http://homepage.ntlworld.com/s.castledine/greenfuz/voxtb_circ.html

I am using 2N3906 for both Q1 and Q2. After assembling it, I tried it out. Hmm... Not really what I was hoping for...

Batt: 9,18
Q1
c 2,87
b 0,60
e 0

Q2
c 6,7
b 2,87
e 2,28
One DMM probe on +, on the battery.

What are the correct voltages in a circuit like this? What changes do I need to make?

I´ve been searching this fantastic site, and the whole internet using many different keywords, bur without a result :-(

Hoping to find an answer this way!

Thanks!

[davebungo]

Well it looks to me like you've got 0.6V across each base-emitter junction - seems OK, and some collector current flowing in each transistor - again OK.  What was "wrong" with the sound?  Did you get any sound out of it?  Did you try adjusting the controls?

[mellowyellow]

It just doesn´t get "fuzzy". If I tweak it to full on both pots, it sounds something like "crunch-fuzz" when I hit the strings really hard. Not what I was expecting. Do you think the transistorvoltages are OK?

As I said before, I´m new to this, and I don´t have a freakin´clue of what might be wrong...

Thank you so much for replying to this question!

Regards
Karl

[petemoore]

Batt: 9,18
Q1
c 2,87  [looks high, I think around 1.15v is 'usual']
b 0,60 
e 0

Q2
c 6,7  [should be near 1/2v of supply...~4.6V
b 2,87  [will be the same as Q1C in properly wired FF...]
e 2,28  [I read yesterday that .8v ...depending if the gain pot is turned up]
  Since it has two Q's I call it a Fuzz Face, Fuzz Face Voltages are posted at ROG or Homewrecker, if not somewhere else.
  I used 470k at the 470 ohm resistor, a few times....very easy to misread a resistor.
  FF's = feedback looped amp stage, are a little trickier to figure because it's a 2 transistor stage, read GEO 'technology of the Fuzz Face' for how the biasing is set up.

[George Giblet]

Are you sure the gain pot is 1k?  it seems like 10k. What about the 820 ohms? make sure it's not 8.2k.