Tyco Octavia Voltages?

[Jazznoise]

Hi all, I've built myself a negative ground version of the Tycobrae Octavia using a 2N5087 as the input BJT and a pair of 2N5088's for Q2 and 3. Can anyone post the voltages they got?  It's gating quite heavily which doesn't surprise me as the base and emittor voltages are so low, also the 1K pot doesn't seem to do much. I tried playing my bass through it and if I used a pick it actually seemed to switch on and off

My voltages are:

Q1

C = 6.1
B = 5.6
E = 1.7

Q2

C = 9.5
B = 1.75
E = 1.11

Q3

C = 8
B = 1.5
E = 0.4

When simulated gave largely the same voltages, though the Emitter on Q3 was at 2 volts. Schematic is here: http://www.freeinfosociety.com/electronics/schemview.php?id=1221 and anyone with any hints as to whats up would be considered cool 4 lyfe.


Full disclosure: I removed C8 and replaced the two resistors with a 1Meg as it looks just like a weird power supply filter and I didn't bother putting the 4 Meg in since it's in parallel with the 680k - I'm assuming that's for switch popping.

[PRR]

> Q1
> C = 6.1
> B = 5.6
> E = 1.7

Well, that can't be right. B and E should be ~~0.6V apart.

I note that B and _C_ are ~~0.6V apart. Could you be misreading/misreporting the pins?

> Q2 E = 1.11
> Q3 B = 1.5

That's funny. Q2E is connected direct to Q3 B...... how can they be different voltages?

I figure (sim "should" say about the same):

Q1 B 3.7V (set by R4 R3 R2)
Q1 E 0.55V higher, 4.2V
Q3 C about the same, 4.3V

Q3 E 1.8V
Q3 B and Q2 B 2.4V
Q2 B 3V

Leaky C4?

Bad layout (output too close to input) causing oscillation?

Lack of C8 filter causing oscillation.

[Jazznoise]

Woops! I always do that, it's the Emitter at 6.1 and Collector at 1.7. 

So your values for Q1's Base and Emitter are correct but when simulated the Collector voltage varies between 1.9 to 1.6 depending on the amount of feedback from VR1.

Q2' reads as
C=9
Base = as above
Emitter = 1.6 to about 1.2.

Q3'
C= 7.5
B = As above, 1.6 to 1.2
E = 3.88 to 3.66 Volts

The last values seem odd to me, the base voltage seems extremely low and the emitter is very high, though I think something is definitely up with my vero for errors. I'm also finding the results from Multisim vary widely, so I'm relutant to rely on it as a source of information!

[PRR]

> varies between 1.9 to 1.6 depending on the amount of feedback from VR1

"VR1"? R8 on the FreeInfo image? That has no effect on DC voltages, because C4 blocks DC.

Also R11 is smaller than R12, should have essentially the same current, so how can it be dropping more voltage?

You got a wiring error somewhere.

[Jazznoise]

Not to necro but just to post saying I resolved the issues. A transistor was upside down and I found a short. Guess a few weeks apart let me eyes see things a little clearer 

It sounds great! I find with the fuzz fully cranked it kinda swamps itself out, but rolled off you get plenty of those nasty ring mod and octave type sounds! Get for chuggy rhythms,  been playing I Wanna Be Your Dog alot with it. Rollercoaster Of Love, too, but that's just because I'm a weirdo.

Thanks for the help, folks.

[Jazznoise]

Going to further necro by adding that my pot was a 10k paralleled with a 1.2k resistor for the gain values.

Use a 10k pot altogether, it gives you a much broader range of tones from weird clangy intermodular to totaly fuzzed beyond beleif. At settings around 8K you not only get an upper octave on the 12th fret, but a lower octave aswell (at least on my version). This is particularly noticable if the volume is rolled off a touch on the neck. Diodes are not matched, if that makes any difference.