Trouble shooting Omega Muff

[crash415]

I'm building an Omega Muff using http://www.runoffgroove.com/omega.html into Jack Orman's http://www.muzique.com/schem/muff.gif

The Muff section works fine.  The Omega section - no sound at all.

The bottom half, left to right is the Omega and the top half, right to left is the Muff.



I've traced the vero layout I did a couple of times and didn't see any issues.

Here are my voltages for Q1 and Q2:
      Q1      Q2
D    4.8     9.1
S    4.1     6.2
G    4.1     4.2

I have the 100k trim pot set at about 30k to get these voltages.  The voltages for Q2 seem to be about what other people have gotten.  But Q1 Source and Gate seem mugh higher than others.  I have tried different 2N5457's and tried reversing the orientation.

Any ideas?

[PRR]

Q1 gate should be at zero.

Q2 gate should be higher than its source.... what MOSFET did you use for Q2?

[crash415]

I have tried both a BS170 and a 2N7000.  Tried a couple of each.  Those voltage readings are with a 2N7000.  I searched the forums and it looks like my Q2 voltages are similar to what others have gotten:
http://www.diystompboxes.com/smfforum/index.php?topic=81273.msg673196#msg673196
http://www.diystompboxes.com/smfforum/index.php?topic=91479.0

[PRR]

> my ... voltages are similar to what others have gotten:

> B Tremblay
> Q1 (J201)
> D: 4.71
> S: 1.27
> G: 0
 
> MetalUpYerEye
> Q1 - 2n5457
> D- 4.75v
> S- 0.87v
> G- 0v

> crash415
>       Q1
> D    4.8
> S    4.1
> G    4.1

Others have Q1 Gate at zero, you have it up at 4V. The schematic only shows gate-to-ground via 33K+22K+500K so we suspect zero is correct.

You also have Q1 S and D jammed against each other (4.8-4.1), others have over 4V difference. A jammed-up device won't pass sound.

> B Tremblay
> Q2 (BS170)
> D: 9.17
> G: 6.16
> S: 4.21
 
> MetalUpYerEye
> Q2 - BS170
> D- 8.3v
> G- 5.84v
> S- 4.02v

> crash415
> Q2
> D    9.1
> G    4.2
> S    6.2

Others have Gate 2V higher than Source. You have Gate 2V lower than Source.

If a (depletion) MOSFET's gate is not a little higher than its source, it is OFF. Which fits the no-sound symptom.

Check path from Q1 Gate to ground.

Check Q1 pinout. It seems same-part can be different pinouts. If you have a fancy meter, Q1 D to S or S to D should be <1K ohms, Q1 G to S or G to D should be "good diode" (or low-R one way, infinite the other).

[crash415]

I know one of the problems:

The Q1 voltage issue was a cut I missed next to R2