SOLVED Pro-10 Green Side - No Output (JFET Pins)

[TAGS]

Hi all!
Just finished the dual pro-10 build, but having an issue with the green side.
The blue side works as expected, but the green side just drops out all signal when engaged.

I've touched up all the solder joints, but no change.
Noticed my Vref is a little lower than expected at 2.8V, for a Vcc of 8.7V.

Any advice from the images below or is the next step just to loop an audio input and walk through the circuit with a multimeter?

Thanks

 

[TAGS]

Am I crazy to think that the source & drain of my JFET are the wrong way around compared to the PCB?
Using a MMBFJ201.

 

[TAGS]

Updating for anyone else having a similar issue...
Flipping the JFET around sorted my issue, but then when I built up the pedal in the enclosure I lost the green side again.
Turns out the tone knob was shorting to the LED Bezel, as a few other people had reported on the forum.

Good luck to anyone searching for answers!

 

[Feral Feline]

How did you "flip" the SMD JFET?

The silk-screen shows the correct orientation, there's really only one way to put it down (2 legs on one side, 1 opposite) — the only way it could be "wrong" is for a manufacturer to stick the Gate on the two-legged side; From what I've read, JFETs are pretty much ambidextrous, in most cases the Source and Drain can be swapped for one-another. I guess this is a case where that's not the case.

I have much to learn yet:

Thread 'Everything You Wanted to Know About JFETs (but Were Afraid to Ask)'

Feb 2, 2022

https://usermanual.wiki/Document/1977NationalFETDatabook.1783250853/view

This is a searchable scan.

Ever wonder why a pedal designer selects a particular part number? See section 2. The datasheets for all of the JFETs we use are in Section 4. There are some interesting circuits in Section 6.

• Chuck D. Bones
• Replies: 13
• Forum: Chucks Boneyard

• 
• 

 

[TAGS]

How did you "flip" the SMD JFET?

The silk-screen shows the correct orientation, there's really only one way to put it down (2 legs on one side, 1 opposite) — the only way it could be "wrong" is for a manufacturer to stick the Gate on the two-legged side; From what I've read, JFETs are pretty much ambidextrous, in most cases the Source and Drain can be swapped for one-another. I guess this is a case where that's not the case.

I have much to learn yet:

Thread 'Everything You Wanted to Know About JFETs (but Were Afraid to Ask)'

Feb 2, 2022

https://usermanual.wiki/Document/1977NationalFETDatabook.1783250853/view

This is a searchable scan.

Ever wonder why a pedal designer selects a particular part number? See section 2. The datasheets for all of the JFETs we use are in Section 4. There are some interesting circuits in Section 6.

• Chuck D. Bones
• Replies: 13
• Forum: Chucks Boneyard

• 
• 

Thanks for the reply.
When I said flipped, I mean from its "belly" to its "back". So the gate stayed in the same place and I was just flipping the source and drain.
You'rE totally correct re the JFET polarity. The OG J201 data sheet said the drain and source were interchangeable, but I didn't see this on the MMBFJ201, so thought it was worth a go.
Perhaps while flipping the FET over I fixed a cold solder or removed a short and it was just a coincidence it worked after!
I think there will always be things to learn about JFETs, but at least I have a shinny new pedal to distract me!

 

[Feral Feline]

I though maybe you meant flipped, but I've only soldered a couple SMD JFETs so wasn't even sure if the legs would reach... but yeah, they're small enough that even with the legs up in the air dead-bug style I can see the solder would reach.

Thanks for the reply and glad you were able to mark this SOLVED!