FOXX TONE MACHINE - Problems

[gtudoran]

Hello guys ... i've run into a problem. I've made a FTM from gaussmarkov.net. No substitutions ware made, except for the transistors: i've used 2n3904.
The problem is this: the overall volume (with the volume pot @ max) is lower then the bypass signal, the fuzz effect is also not so strong as Tonebender but that is no problem afterall, and the octave up effect is not so strong like in this clip for example: http://www.youtube.com/watch?v=0Zl68eu8s1k

The voltages are this:
       Q1     Q2      Q3        Q4
E   0.13    1.54    0.18     0.15 
B   0.70    2.17    0.75     0.72
C   2.16    6.80    6.60     7.36

As far as i see... is only a problem with Q4 (according to GGG site): Q4's B is higher then E ... and i think that is not quite right. I've checked and double checked the resistor from Q4's E and is 1.5K... so according to schematic the transistor is polarized in the right way... but according to field data.... is not.

Any hellp will be appreciated.

Best regards,
Gabriel Tudoran
Analog Sound

[jdub]

I assume your 2n3904s are oriented correctly, with Q4 emitter to 1k5 to ground?  Have you checked for solder bridges in that area?

[gtudoran]

Acording to Data Sheet 3904 have EBC from left to right with flat side oriented tword you... so yes they are oriented ok. No solder bridge... i've bypased the 1k5 resistor and the amplification went up but ... there is a lot of noise... and of course no tone as the one from the clips... strange... very strange....

Best regards,
Gabriel Tudoran
Analog Sound

[jdub]

Now that I think about it, isn't the emitter supposed to be a diode drop lower than the base, as yours is?  I checked with the GGG site, and it may be possible that JD accidently reversed the readings for B and E for Q4:  Q1-Q3 all have their readings listed in order C-B-E, while Q4 is listed C-E-B.  E and B might have been reversed unintentionally.

If this is the case, you may have a different problem.  I'll check my own voltages and post back.

[gtudoran]

Thank you jdub, i will try also to see if there is smth wrong with my build... but so far everything seems ok.

Best regards,
Gabriel Tudoran
Analog Sound

[jdub]

Checked the voltages on mine, and the emitter should indeed be a diode drop (.6v) below the base- GGG has 'em reversed.  So your voltages for Q4 appear correct.  Your problem, therefore, would seem to be elsewhere.  Have you audioprobed?  Checked offboard wiring? 

[gtudoran]

Thank you jdub - the problem is this: at the output i have unity gain ... but i do have some hot pickups... and this should be a problem. As far as i saw fuzz fx have a volume drop. I will build a fet or transistor booster after the fuzz and use the gain pot from the booster as overall volume, i think that will solve my problem.

Best regards,
Gabriel Tudoran
Analog Sound

[jdub]

Well, my FTM seems to have pretty good output, so I'm not sure about your volume drop...have you checked your volume pot?  They can be dodgy sometimes...how about the octave? Sound OK?

[gtudoran]

Hey guys ... i'm the king of idiots; please remember that 1nF is not equal to 1uF... so the only capacitor that had 1nF value i've replace it with 1uF... that was the problem.
For the record it works ok with 2N3904 and/or BC548/BC549.
The Ge diodes that i used ware EF series (germanium diodes used for radio detection)

Best regards,
Gabriel Tudoran
Analog Sound

[jdub]

Easy to make cap value mistakes- you're not alone.  Glad you got it working!