Son Of Ben Q2 Biasing Issue

[Stephenthegun]

I built the Son of Ben and used what are probably not genuine J201's. I got the biasing close but not quite on Q1, however, Q2 and Q3 were in the low 3v range. The pedal sounded good, but I was hoping I could make it better, so I ordered the surface mount J201's. I installed them today and got Q1 and Q3 bang on at 5.1v and 4v but now I cannot get Q2 to drop below 9v. With the trim pot all the way down Q2 reads 9.10v and with it all the way up it reads 9.15v. What have I done? Help!

 

[music6000]

Yes, P503.

With DMM on Volts, Black probe on Yellow circle & Red probe on Red circle, adjust Trimmer, it should go from aprox.1.5v to 9v!

 

[Stephenthegun]

With DMM on Volts, Black probe on Yellow circle & Red probe on Red circle, adjust Trimmer, it should go from aprox.1.5v to 9v!

I am not getting much of anything at all when I do this, only a few mV. Do you think my trim pot is bad?

 

[music6000]

I am not getting much of anything at all when I do this, only a few mV. Do you think my trim pot is bad?

Try putting a temporary 27K resistor or something close from Red circle to Yellow circle.
With Black probe to Ground, Test voltage on yellow circle.

 

[Stephenthegun]

Try putting a temporary 27K resistor or something close from Red circle to Yellow circle.
With Black probe to Ground, Test voltage on yellow circle.

I soldered on the temporary resistor and once again got no change in voltage.

 

[music6000]

I soldered on the temporary resistor and once again got no change in voltage.

Was this with the transistor Drain leg disconnected from the yellow circle?

 

[Stephenthegun]

Was this with the transistor Drain leg disconnected from the yellow circle?

no the drain leg was not disconnected. I will do that and try again.

 

[Stephenthegun]

Was this with the transistor Drain leg disconnected from the yellow circle?

I disconnected the drain leg and got the same result.

 

[music6000]

I disconnected the drain leg and got the same result.

Are you using a good quality Digital Multi Meter, It has to change or your defying the physics of electronics!

 

[Stephenthegun]

Are you using a good quality Digital Multi Meter, It has to change or your defying the physics of electronics!

The multi-meter has never given me trouble before, I am most likely just a moron. I will go back and do things again.

 

[Stephenthegun]

I tried the multi-meter again and got the same result. Have I done something wrong?