help troubleshooting

[mlhuff]

I recently purchased and built a tycho brahe clone from general guitar gadgets. I get sound when the pedal is off. But when i turn it on, nothing. I am new to this and would like some help. I have looked up articles and videos but I havent found anything to help me trace the signal through the pcb and what voltages I should be getting.
Any help with this would be appreciated

[GibsonGM]

Hi ML, welcome!

Go here, read this, and see if you can provide the info requested back here in your post.  That will get us started   
These things are usually a builder error, poor soldering, the wrong part put in the wrong place and so on.  Taking it thru the process will help figure out what's going on!

https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[thermionix]

Just noticed something odd, won't help OP though.  The GGG schematic has Q1 backwards (it works either way), but it is correct on the actual PCB they sell.

[GibsonGM]

Good find. 

Might as well toss this in here too, how to make an audio probe to trace the circuit, since OP asked about it.
https://www.diystompboxes.com/pedals/debug.html

[PRR]

...The GGG schematic has Q1 backwards...

The schematic is correct as drawn. The as-drawn power supply is Negative hot, POSitive ground. The gizmo is a feedback pair, complementary NPN-PNP, with a Darlington in the PNP position. Q1 should be a NPN and should be in normal mode (not inverted).

To show the action I have re-drawn without the AC parts, without the Darlington frill, so reduced resistors around Q1. It biases-up fine. Q1 forces Q2 Collector to follow Q1 Base, nearly. All polarities are correct.

Making the 2nd stage a Darlinton, making a 3-stage amplifier, allows making Q1 a higher impedance, more suited for guitar.

If you are saying Q1 should be "inverted" (C and E swapped), that would negate much of the advantage of a 3-stage amplifier, lower the input impedance. It may not be significant, depending what drives it.

[thermionix]

The as-drawn power supply is Negative hot, POSitive ground.

I'm aware, but the actual Tycobrahe Octavias had Q1 (NPN) installed the "wrong" way with emitter toward (+) ground.  The circuit runs either way.  This schematic matches the 70s originals, and the GGG PCB:

[italianguy63]

The as-drawn power supply is Negative hot, POSitive ground.

I'm aware, but the actual Tycobrahe Octavias had Q1 (NPN) installed the "wrong" way with emitter toward (+) ground.  The circuit runs either way.  This schematic matches the 70s originals, and the GGG PCB:

+1

We had a thread on Q1 orientation sometime back..

Yes, the orientation works either way  (verified by me).. for what that is worth!

MC

[mlhuff]

Thank you for the suggestions. I am reading up on what I need and building an audio probe. Trying to find an electronics store near me. Once I have this info I will post results