BSIAB2 Problem, please help!

[juan_felt]

Hi, I just finished making a GGG BSIAB2, but I get no sound when the effect is on. Bypass sounds perfect. I checked all the transistors, and I realized that 3 of them where inverted. Instead of using the 2N5457 I used BF245A. I placed them in the right position and the voltage readings started to make some sense, but still no sound. At one point I lifted the PCB to check all the solders again and I must have accidentally touched the solder part of  Q5 and the pedal started working! This transistor is the one that had the weird readings, I tried touching the pins with a screwdriver, and when I shorted pins G and S it worked.

Why Could this be? Thanks!

[juan_felt]

Here are the readings,

Q1
D=5.1
S=0.7
G=0.01

Q2
D=9
S=5.1
G=3

Q3
D=4.3
S=0.75
G=0.3

Q4
D=8.9
S=4.4
G=3

Q5
D=8.6
S=1.94
G=0.02

[Pyr0]

Your Q5 voltages are off from the GGG recommended voltages. It's not biased right.
Have you tried adjusting the 100k trim pot to get roughly 4 volts on the drain of Q5 ?

[juan_felt]

Your Q5 voltages are off from the GGG recommended voltages. It's not biased right.
Have you tried adjusting the 100k trim pot to get roughly 4 volts on the drain of Q5 ?

Yes, I tried, but the voltage lowers almost nothing.

[Pyr0]

Double check component values for R14 and R15, also check that area for good solder joints and the q5 soldering and orientation.

[juan_felt]

The values are OK. At first sight everything seems to be fine. It's weird that it worked when I shorted the G and S ends of the transistor... 

[Pyr0]

It's not really weird at all, that transistor is not correctly biased, so it's not passing and amplifying the signal from gate to source, when you shorted out G S you bypassed the transistor and the signal came through. At least it looks like everything else is working up to that transistor. Keep looking in that area, maybe even a small solder bridge somewhere between tracks, or an open circuit on some component where it's not properly soldered.

[juan_felt]

Good, now I know! I'll triple check the area again and see what happens. Thank you! (I'll be back with what happened!)