Green Bean transistor problem?

[zilla]

Hi All,

I am in the process of debugging my Green Bean pedal.

I have traced the signal up to Q1. there is an audio signal on the base, but nothing on the collector going to C2 ad onto the IC.

I tried swapping Q1 and Q2 with the same results... no signal is making it past Q1.

I also touched up the sockets for Q1 but it made no difference.

on an unrelated (?) point, i noticed that the area around where the DC power comes onto the board and C11 is quite warm/hot. Is it supposed to be like this?  The polarity of C11 is correct on the board (just double checked it as i was typing this

Voltages on Q1:
E: 0 V
B: -0.37 V
C: -0.75 V

I don't think this is right? 


Any help would be appreciated.

Tim

[DutchMF]

There is an issue with your power supply. You should get Vc (close to +9V) on the collector of Q1, while you're measuring a negative voltage there. Same thing goes for the base, that should read positive as well. Start with checking all the wiring, part values and connections for the power supply section, and we'll take it from there!

Paul

[hammerheadmusicman]

What transistors are you using?

[RobA]

Did you make any substitutions?

It sounds like either there is a short near the power input or the DC jack is wired reversed. If it's R17 and D6 heating it's pointing to a power issue.

[zilla]

No substitutions. Everything is as in the BOM.

I will double check the power connections and will report back.

Thanks

[hammerheadmusicman]

Some hi res pictures needed on both sides, I think.

George

[Vallhagen]

Check the power filtering components. Especially the direction of D6 (my first guess is that component). Next guess; is the power jack correctly wired? Pin shall be negative.

Look at it this way: all components before Q1 are passive->you shall have signal on Q1 input (base) even with no power connected. And as mentioned above, you shall be very close to 9VDC on Q1 collector.

Cheers

[zilla]

stupid me.. .i had the positive and negative terminals flipped.  everything is working 100% now.  thanks!


unrelated question:  i noticed that there are two holes in the PCB that are not used (between C12 and lug 1 of the tone connection) and under the IC.  what are these holes used for?

[RobA]

Glad you got it figured out, congrats!

I don't have a board in front of me, but I'd guess that they are vias. Vias are just connections between the layers. If you look at the board and the trace connects to the hole on one side and then continues on the other side, it's a via.