debrad
Active member
Before installing my Two Tone Fuzz board in its enclosure...I loaded it up with 3 silicon PNP transistors just to make sure it worked (I'm waiting for some PNP Ge transistors to arrive but it might be a while given our current postal strike here in Canada...). The silicon PNPs came from SmallBear and were identified as 2023AN2.
I fired up the circuit and it sounded nice and "Tone Bender-ish" in the 2 transistor mode but didn't make any sound when I toggled to the 3 transistor mode.
This sent me down a relatively shallow rabbit hole of debugging but I couldn't seem to find anything wrong with the build itself so my next step was measuring voltages to make sure Q1 was getting power. Regardless of whether the mode switch was set to 2 transistors or 3, I had the following:
Input = 8.83v
Pin5 of TC1044SCPA = -8.56v
R3 (10k) = -8.56v on both sides
Q1 collector = -8.56v
Q1 base = 0.00v
Q1 emitter = 0.00v
Q2 collector = -1.458v (bias fully CW).....-7.23v (bias fully CCW)
Q2 base = -0.592v
Q2 emitter = 0.00v
Q3 collector = -2.147v
Q3 base = -1.458v
Q3 emitter = -0.835v
Knowing that I had already tried a few different 2023AN2 silicons in Q1, I decided to test one of my random germaniums in it's place (black "top hat" style can with "GE" in script on the top and "D3" written on the supplier's baggie). With that installed, I measured the following:
Q1 collector = -8.44v
Q1 base = -0.05v
Q1 emitter = 0.00v
Despite the VERY small difference in the voltage readings, I suddenly had fuzz in both the 2 transistor and 3 transistor mode settings (and a discernible difference in the character of each!).
Is it possible that the original PNP silicon transistor just didn't have the proper specs to function properly in the Q1 position? If that's the case, is it odd that the same type of transistor appeared to work sufficiently in Q2 and Q3?
I fired up the circuit and it sounded nice and "Tone Bender-ish" in the 2 transistor mode but didn't make any sound when I toggled to the 3 transistor mode.
This sent me down a relatively shallow rabbit hole of debugging but I couldn't seem to find anything wrong with the build itself so my next step was measuring voltages to make sure Q1 was getting power. Regardless of whether the mode switch was set to 2 transistors or 3, I had the following:
Input = 8.83v
Pin5 of TC1044SCPA = -8.56v
R3 (10k) = -8.56v on both sides
Q1 collector = -8.56v
Q1 base = 0.00v
Q1 emitter = 0.00v
Q2 collector = -1.458v (bias fully CW).....-7.23v (bias fully CCW)
Q2 base = -0.592v
Q2 emitter = 0.00v
Q3 collector = -2.147v
Q3 base = -1.458v
Q3 emitter = -0.835v
Knowing that I had already tried a few different 2023AN2 silicons in Q1, I decided to test one of my random germaniums in it's place (black "top hat" style can with "GE" in script on the top and "D3" written on the supplier's baggie). With that installed, I measured the following:
Q1 collector = -8.44v
Q1 base = -0.05v
Q1 emitter = 0.00v
Despite the VERY small difference in the voltage readings, I suddenly had fuzz in both the 2 transistor and 3 transistor mode settings (and a discernible difference in the character of each!).
Is it possible that the original PNP silicon transistor just didn't have the proper specs to function properly in the Q1 position? If that's the case, is it odd that the same type of transistor appeared to work sufficiently in Q2 and Q3?
