Slow Loris low volume

[murdog47]

So I've finished up a slow loris and the effect sounds correct.  However the volume is really low.  I probed the circuit and found that I am losing volume at C12.  As the signal hits C12 it is at what I feel is a correct volume level but then it drops significantly on the pad on the other side.  I took out C12 thinking it was the Cap but it did not change with a new cap.  I ran a jumper wire across thinking the signal would stay the same without a cap in but it doesn't still drops? I'm still new to this but the only thing I can figure is that the components after C12 are causing the volume drop, yes?

[murdog47]

DCV as follows

IC 1:8.65
    2:4.86
    3:4.41
    4:0.00
    5:-24.2
    6:4.85
    7:9.31
    8:4.96
Transistor Q1
1:9.31
2:8.95
3:8.95

[mgwhit]

Check to see that your R8 is really 1M.  I don't think C12 is causing your volume drop, but i do wonder if you have too little resistance in your path to VB.

Or I suppose you could have a bad JFET.  Did you use a 2n5457?  I'll check my voltages after I put my kid to bed tonight.

[murdog47]

I checked all my parts values and they are correct. Used a 2n5457 for Q1. That would be great, Thanks!

[mgwhit]

Etched or fabbed board?  If fabbed, pre- or post-April 2012 version?

[murdog47]

Fabbed post correction

[mgwhit]

Here are my voltages:

IC1:

1: 8.94    8: 4.72
2: 4.63    7: 9.59
3: 4.21    6: 4.64
4: 0       5: 0

Q1:

D: 9.59
S: 0.98
G: 0

I'm confused by my own JFET Gate voltage -- I assumed it would be close to VB -- so apparently I'm missing something.

I'm wondering if you have a bad 2N5457.  You have confirmed it's not backwards, haven't you?  If replacing the 2N5457 doesn't help, the best thing you can do is upload some good photos of both sides of the board.  Good luck!

[stecykmi]

is C8 correct? try removing it altogether and see what happens. It acts as a low pass filter (in other words, a high end cut); by removing it, it'll disable the cut control, but the effect should essentially work.

[murdog47]

The trans is facing the correct way. I guess I should ask, does it make a difference in regards to the voltage readings, which position the toggle is in? I had the LED's selected when I measured mine.  I have a couple extra 2n5457's think I'll just replace it and see what I get.

[mgwhit]

I guess I should ask, does it make a difference in regards to the voltage readings, which position the toggle is in? I had the LED's selected when I measured mine.

Nah, shouldn't matter.  The DC on the IC and the JFET Gate is blocked from the clipping diodes by coupling capacitors (C7, C12).

[murdog47]

And the culprit is.........a bad JFET. Replaced it and all is right with the world. Thanks for the help! 

[madbean]

They are finicky devices. Glad you got it worked out.

[mgwhit]

And the culprit is.........a bad JFET. Replaced it and all is right with the world. Thanks for the help! 

Cool.  Glad you found it!