Dr. Boogey debug assistance needed

[therecordingart]

I'm not sure if I should scratch my head or pull my hair out on this one. I've gone over the PCB at least 50 times looking for shorts, improperly oriented parts, and general mistakes.

1.What does it do, not do, and sound like? No output and the trimpots don't change the voltage to bias the fets.
2.Name of the circuit = Dr. Boogey
3.Source of the circuit (URL of schematic or project) = http://gaussmarkov.net/layouts/drboo/drboo-project.pdf
4.Any modifications to the circuit? No
5.Any parts substitutions? 2k mid pot and 500k gain pot
6.Positive ground to negative ground conversion? No
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 8.75 volts
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead = Not set up this way
Voltage at the circuit board end of the black battery lead = Not set up this way

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
D = 8.57v
S = 235mv
G = .7mv

Q2
D= 8.56v
S= .4v
G= .7mv

Q3
D= 8.6v
S= 384mv
G= .1mv

Q4
D= 8.6v
S= 258mv
G= .1mv


Q4
D= 8.6v
S= 8.1v
G= 8.6v


D1
A (anode, the non-band end) = 0.1mv
K (cathode, the banded end) = 8.75v

[flintstoned]

I had the same problem with the trimmers, I ended up tying one leg to ground. I haven't yet worked on a solution for biasing the fourth yet since its tied to the emitter of the fifth. My perf is starting to get messy, and I dont know if i can squeeze another trimmer in there for that fet and I don't know how well that would work out. Plus I just get too busy with other projects and it gets pushed back further on the workbench.

[Schappy]

Build an audio probe and probe through the circuit starting at the input.

[therecordingart]

Build an audio probe and probe through the circuit starting at the input.

I can do that, but will that help me figure out why I can't bias it?

[jkokura]

Yes.

But it sounds to me like you've either got a bad solder connection around the trimmers or perhaps a backwards part somewhere. I've built this pedal, and it worked fine for me. Any chance we can get good pics of the front and back of your board?

Jacob

[Brymus]

Yeah your voltages are askew.
You should be able to bias them to half of your V+
And Q4 is way wrong,something is possibly shorted around there as you have 8V on all 3 legs of that FET

[John Lyons]

I think the board isn't getting ground somehow.

[therecordingart]

Thank you to everyone. I'm going to sit down with it again today to see if I can get this figured out. All of your help is much appreciated!

[gtudoran]

Look carefully at the ground-plane if you use gaussmarkov PCB, i had a problem once with the ground connections.

Best regards,
Gabriel Tudoran
Analog Sound

[therecordingart]

Look carefully at the ground-plane if you use gaussmarkov PCB, i had a problem once with the ground connections.

Best regards,
Gabriel Tudoran
Analog Sound

If I can't figure this out I'm ready to tear it apart and use MadBean's layout. My non-working pedal is totally my fault and not the fault of gaussmarkov's layout, but at the same time I didn't feel very good about the layout from the start.

[geertjacobs]

Don't pull it apart just yet!

I had a similar problem with my DR Boogey and one of my J201s was broken.
Probably overheated when soldering.
Try replacing the JFET and recheck.

First get the voltages right.
And then as suggested before: use an audio probe to see where your signal is lost.

[therecordingart]

Found one issue. Small Bear sent me 100ohm trimpots...found a 100k at work and was able to bias a fet so now I need three more. We'll see where it goes from there.