Sparkplug Feedback/computer noises

[lespauldoc]

Ok, just curious if there are any ideas.... I've built several Sparkplug v1s, and loved them. This rev1 is my first time building the update. So it works great OUTSIDE the box (rock it before ya box it!) with the exception of picking up a radio station. I box it and it immediately starts feedbacking this "WEEEEEEEEEEEEE" noise that gets worse as you turn up vol and gain. You can hear the guitar signal through the noise, but the "WEEEE" is pretty overwhelming.

I've unboxed and reboxed 3x now, also double check ground, solder points etc.... This is far from my first build, and I'm perplexed. Any ideas?

[midwayfair]

Audio probe and see where it gets introduced.

[lespauldoc]

I built an audio probe, any links to how it works/how to debug with one?

Thanks!

[madbean]

It's very straight-forward. Plug in the effect to your testing rig. Ensure the PCB has power and the fx input is getting guitar signal. Don't connect the fx output, and use the audio probe to test for output on the components. For IC-based effects, test the inputs and outputs.

For the Sparkplug, this would be pins 3, 1, 5 and 7. You will not hear any signal on pins 2, 6, 4 or 8 (this is normal).

[PhiloB]

I pick up some RF stuff with my Sparkplug when I'm at church sometimes.  But sometimes I don't.  Curious to see what you come up with.


Sent from my iPhone using Tapatalk

[lespauldoc]

Well, i removed the IR transistors and put in 2n7000s (matching pins correctly). Some noise (as expected) unboxed but pretty decent. So, I'll see if that helped. Even screwing in there before the transistors gave tons of noise. This is my first time using the large military grade transistors, so maybe I damaged them clipping the top? I dunno. I'll box this and I'm building another Sparkplug for my bro-in-law for Christmas. I'll compare the 2 if they work out: 1 with 2n700 and the other with the IRs.

[lespauldoc]

Any idea-- the IRF transistors must've been the culprit. Pedal works perfectly (and sounds awesome) with 2n7000. Weird? I know I double checked the pinouts to make sure. I can only guess I may have damaged them when i clipped them.
Thanks for the help!