Stompbox not working
Figure 1. Dry joints. Fix these first.



Figure 2. Debug test points.

Connect multimeter probe to GND for all voltage measurements. 


Confirm 9 V at (1).
Connect the Mammoth GND to your amplifier audio GND. Using your amplifier jack lead as a test probe, touch the tip at (2) and strum the guitar. Turn the volume down first as there will be a DC thump when you connect. You should hear the guitar on the amp. [OP reports 0.54 V at (2).]
Measure the DC voltage at (3) and (4) and write it down. It should be somewhere between 3 and 6 V. [OP reports 1.2 V at (3) and 0.58 V at (4).]
Try your audio probe at (3) and (4). 
Try the audio probe at (5) and (6). [OP reports audio at (6) but not on output.]


With all pots maxed it gives .54V at point 2, 1.2V at point 3 and .58V at point 4

Basically you've got to trace through the circuit and find where the signal gets lost. Report back with your findings.




  OP: I'm having sound that I expected to be even at point (6), but after the 10K pot there's silence.


If you're getting signal at (6) then you're nearly there. Wire the output directly to (6) and see if the box works. If it does then the problem is (a) connnection to the pot, (b) a faulty pot or (c) connection from the pot.