Graphite Distortion

[almostjay]

Hey all. I am trying to finish up my Graphite Distortion build. I have the pedal built and it works, but the distortion pot does not affect the distortion level at all. I measured the resistance on this pot and it’s perfect while out of the circuit but as soon as I touch it to the pads it measures short.

I populated the “modern” section (and everything else) and I’m now wondering if I was supposed to leave some other parts unpopulated if using the modern section?

Any other ideas?

I’ve attached a picture of the build. It went pretty cleanly. Could my issue be those socketed transistors?

 

[Nostradoomus]

Can we see the bottom of the board? Some of the top side soldering looks not so good. Where is the CMOS chip from? What IC is in the bottom spot?

 

[jwin615]

Legs 2 and 3 are shorted
Check leg 2 to 1
Even then, jfets/cap in the feedback loop may be giving a false reading

 

[jwin615]

What jfets are used? The 3819 has gate on pin 2
If you used something with a different pinout, like a 201 or 5457, that'll do it.
You can test this theory by pulling the jfets.

 

[jwin615]

Also, there's no reason to socket these jfets unless you think you'll toast them.
When you short the gate and source, they're just diodes, essentially.

 

[almostjay]

Can we see the bottom of the board? Some of the top side soldering looks not so good. Where is the CMOS chip from? What IC is in the bottom spot?

I can post a picture of the bottom tomorrow. The CD4069 is from stompboxparts and the op amp is a TL071.

 

[almostjay]

What jfets are used? The 3819 has gate on pin 2
If you used something with a different pinout, like a 201 or 5457, that'll do it.
You can test this theory by pulling the jfets.

That might be it. Good call. Will test tomorrow thank you!

 

[almostjay]

Can we see the bottom of the board? Some of the top side soldering looks not so good. Where is the CMOS chip from? What IC is in the bottom spot?

Legs 2 and 3 are shorted
Check leg 2 to 1
Even then, jfets/cap in the feedback loop may be giving a false reading
View attachment 113059

Here’s a picture of the bottom of the board. It’s been awhile since I populated it. I remember now that the reason why I socketed the transistors was that I didn’t have any 2N3819s, I used some 2N5457s instead. Is that the issue?

Thanks guys!

 

[jwin615]

Yup. 5457 is DSG
3819 is SGD
Try spinning them 180
Edit, or just pull them out and see if the pot functions

 

[jwin615]

Nope, spinning won't work I don't think
Have to get the gate to the center pin.

 

[almostjay]

Appreciate it. This is exactly why I socketed them! Should have thought of this myself.

 

[jwin615]

Jfet is a single one junction device
If you look at the symbol, and squint, it's a diode symbol with 2 cathodes(source and drain). This wasn't by mistake.
Any jfet with a gate in the middle should work, or twist em.