Okay, just boxed up a Tonebender Mk III (
layout) - used 1T308B in Q1/Q2 (61/81, 0 lkg) and an MP21D in Q3 (120 hfe, .19 lkg) - and a D9V for a diode. I'm using the negative voltage inverter daughterboard in the enclosure. I also did the volume mod - replaced the 220k resistor at the upper right of the board with a 68k and upped the volume pot to 250k.
It sounded great BEFORE I boxed it, hooked up to my test rig. Got it boxed, and hooked it up to my cheapo Squier Strat to test - and whenever I turn the guitar volume up past 80% or so, the volume drops way below unity and the fuzz get's really splatty, as if the transistors are mis-biased.
Granted, hooked up to my test rig I never opened up the volume, but even when I turned it up to ~50% I didn't get the volume drop/lo-fi fuzz effect.
I'd check voltages, but I don't think it has to do with the transistors - I have a Mk3 test rig with sockets so I can test transistor combos, and they seemed to work fine in that. The only difference is the diode - I have a 1N270 hard-wired in the rig.
Any suggestions on what I should look for?
EDIT: Swapped out the diode for a 1N270, then a 1N34, then tried a different MP21D (hfe 110, lkg .28). Same thing each time - sounds awesome until I turn the guitar's volume past 8 on the dial. Then the same behavior.
EDIT #2:
Bias Voltages.
Q1
e - 8.59
b - 8.89
c - 8.61
Q2
b - 1.34
e - 8.32
c - 4.89
Q3
e - 0
c - 3.3
b - .069
Locked
