Son Of Ben Preamp Debugging

[pablonavarrob]

Hi everyone,

I already posted on facebook for help, but trying my luck here just in case some more of you can take a look at this issue.
I've been holding off until now to attempt to build a Son of Ben pedal. I built everything according to the guide, been reading a lot about this build and attempted it on Sunday.

Once I plugged it in, I noticed that there is indeed sound coming through bypass mode, but, when I turn the effect on, there is nothing. Only some light hizz from the amp itself as far as I can tell. I cannot see any bridges or anything weird in the board. I have checked twice all the components before installing them. I don't have a multimeter at hand right now, will be getting one in a few days, but in case someone sees something obvious that I am not noticing, please let me know, I'd be very grateful, this is a pedal I've been wanting to build for a long time.


I think there might actually be either a broken component or a bridge, because if I touch the OUT pin in the board, the one going to the footswich, there is noise coming through the amp which changes character as I move the pots. I just got a multimeter and tested the value for all resistors, which match what is specified on the build docs. Edit: I also made sure to bias the J201 to 4.5-5V.

Any ideas?

Adding some pictures below, lmk if you need anything else.

 

[Brett]

I’d recommend starting by reflowing your solder joints. The pictures may be deceiving, but almost all of the solder joints on the bottom row look questionable.

I’m not sure how long you’ve been soldering, so please take this as constructive criticism: Try turning up your iron, spending less time per joint, and use a bit less solder.

 

[Laundryroom David]

Biasing this one is also a bit different than the ‘typical’ fet-based drive pedal. The trimpot with Q1 needs to be set to 2k ohm (ie resistance). Then you can bias Q2 and Q3 to 4v at the drain of each.

But before we get there - are you absolutely certain about the pinout of your J201s?

 

[pablonavarrob]

I checked today all solder point and the biasing as suggested. As per the pinout, 99%. I have checked several other finished builds and all use the same pinout as mine.

I am not sure what might be wrong to be honest. Checked with the multimeter the resistance values and the capacitors, so didn't make any mistakes there.

 

[Robert]

Where did you get your J201 transistors?

 

[pablonavarrob]

Banzai Music, a seller here in Germany

 

[Laundryroom David]

I checked today all solder point and the biasing as suggested. As per the pinout, 99%. I have checked several other finished builds and all use the same pinout as mine.

I am not sure what might be wrong to be honest. Checked with the multimeter the resistance values and the capacitors, so didn't make any mistakes there.

Different manufacturers have different pinouts of the transistors. Can you post a clear pic of the flat face of the J201s?

 

[jwin615]

Have you checked your switch to ensure it's not borked from overheating?
Sure you didn't reverse your in and out cables when testing? Will still work in bypass. Ask me how I know...