Lectric-fox Flintlock: Losing Audio

[pbrommer]

Usually I can troubleshoot okay-ish, and have a Flange with No Name board working, but this one is stumping me. I’ve ran an audio probe through the circuit: step 1, passes through with bypass off. step 2, I lose audio in the circuit.

My goal was to make sure the audio portion worked before tackling the trimpot calibration. I’ve zoomed in on the trouble spot

The problem seems to be that I have audio on the upper part of R22, but then nothing on the other side. I pulled it, checked it (22k — correct) and put a 20k in (what I had on hand). Still has the same issues. Q1 measured all at 7.05V, but then when I removed it, the Gate voltage dropped to 4.5ish.

Ideas? I did scour Madbean and other forums, but no dice. Thanks

PS learned that you can’t use a mn3207 with 15V - it makes mn3207 sad.

Link to file to look at schematic, etc: Flintlock

 

[pbrommer]

Usually I can troubleshoot okay-ish, and have a Flange with No Name board working, but this one is stumping me. I’ve ran an audio probe through the circuit: step 1, passes through with bypass off. step 2, I lose audio in the circuit.

My goal was to make sure the audio portion worked before tackling the trimpot calibration. I’ve zoomed in on the trouble spot
View attachment 92617
The problem seems to be that I have audio on the upper part of R22, but then nothing on the other side. I pulled it, checked it (22k — correct) and put a 20k in (what I had on hand). Still has the same issues. Q1 measured all at 7.05V, but then when I removed it, the Gate voltage dropped to 4.5ish.

Ideas? I did scour Madbean and other forums, but no dice. Thanks

PS learned that you can’t use a mn3207 with 15V - it makes mn3207 sad.

Link to file to look at schematic, etc: Flintlock

Okay, bumping this back up. I can hear flanging, but it’s distorted (hasn’t been calibrated). If I short out r22 (22k which feeds into the gate), I get sound and passes through. Voltages seem to hover at all pins of the FET (J113) about 6.5-7.0V. The 1M that connects the drain and source together (and connected to one of the voltage dividers) doesn’t seem to have sound.
I’ll try some different FETs, but if anyone has an idea or thoughts, I’d appreciate it. Kind of stumped (but I got the ? flange from deadend running ). Thanks everyone

 

[jimilee]

I’m guessing you’ve already reflowed all your solder joints and checked your parts values etc.

 

[pbrommer]

I’m guessing you’ve already reflowed all your solder joints and checked your parts values etc.

Yep. Did that. Might just do a bit of adjustment by ear with the 22k/FET/1M section until it works.

 

[KreoPensas]

Hmmm. I have this in a pedal, and another board not built.

I have questions about your mn3207 comment... sounds like a thing learned by doing, and I have to wonder if it took anything else with it.

 

[pbrommer]

Hmmm. I have this in a pedal, and another board not built.

I have questions about your mn3207 comment... sounds like a thing learned by doing, and I have to wonder if it took anything else with it.

I nuked the mn3207. I can get sound through the pedal with a MN3007, but only if I jumped from the band of the diodes over past the FET.
Also, I can only get the frequency from 69.9k to about 2.2Mhz. But I think my meter is butt, so might have to roll with it.
I replaced the 1M (r24) and the r22 (15k) and still it’s not great. The diodes really distort any sound coming from an iPad out of the pedal (for testing). I’m getting there, but about ready to punt the pedal to someone because [insert swear words]. I know I’ll get it but …

 

[KreoPensas]

I am sorry, I know I feel it hard every time. As bad as losing a pet.

I would just replace the jfet and diodes just because I roll like that. Your mileage (and roundness) may vary.

 

[pbrommer]

Okay, here we go. New 2n5457. Have sound through the pedal! But it’s really really muffled.

So far, I have the clocks and frequency calibrated, but I’m still losing audio/minimal output right around Q1. I did replace the diodes, checked the resistors, etc. I had just temporarily put the 2n5457 in and got sound through. But it’s not getting enough to match the bypass signal. Almost ready to 1) direct wire the components together to cover up for a pcb break or 2) jumper from the diode output in the audio section past the FET to the next opamp.

Thoughts? Voltages are good (though I have 7.05 volts rather than 7.5v because the power supply is right at 9.0V) etc.