Author Topic: major hum and radio interference on SLD  (Read 326 times)

aldaraia

  • Diode Destroyer
  • *
  • Posts: 6
    • View Profile
major hum and radio interference on SLD
« on: February 14, 2017, 05:54:42 AM »
got one of keefe's sounds like doom projects, put it together yesterday which was rough, but only because i vastly underestimated the difference between an etched single sided board and the double sided, two layered boards i'm used to. after some serious debugging, i got it working in the sense that it passes signal and all of the knobs and switches work, but there is some SERIOUS radio interference and hum coming from it.

here's all the info i have after experimenting for a bit.

  • radio interference is only there when my guitar is plugged in but the volume is all the way down.
  • hum goes away when I touch the pedal enclosure, more so when I touch both my strings and the pedal
  • both hum and radio interference are present when using an isolated power supply, as well as with a 1spot (didn't wire a battery)
  • it is definitely a notable amount of hum compared to the other fuzzes and distortions on my board
  • it is probably not the shielding on my guitar as all cavities are shielded with copper tape
  • it is also probably not the shielding on my leads as the hum and interference are not present with other pedals, and i use high quality connectors and cable for my guitar leads

i did some searching around the forum but i got nothing conclusive, and most of what i did get was that it was the cables or the guitar which, at this point, i've all but ruled out.

i thought maybe it would be my dc jack, as I'm not using one with a battery terminal, but i soldered a wire from the ground of that to the enclosure and that didn't help. I have not attempted running a wire from ground to ground on the input jacks but i checked continuity between them with my multimeter and they are both fine, but i'm willing to explore this option.

i don't have any 1000pf caps on hand to try putting one between input and ground, but i do have to make a trip to the electronics store today so i can pick one up if that's what appears to be the favored method of dealing with this.

any input or suggestions would be lovely! when playing, there is no discernible hum or interference and it sounds super super great, i'd just like to be able to count it among my very quiet other pedals. this is my first build in a long while so i'm just getting back into the swing of building and debugging.

Matt

  • Electron Doctor
  • *****
  • Posts: 590
    • View Profile
Re: major hum and radio interference on SLD
« Reply #1 on: February 14, 2017, 02:07:13 PM »
It'll help if you post some pics
Matt

aldaraia

  • Diode Destroyer
  • *
  • Posts: 6
    • View Profile
Re: major hum and radio interference on SLD
« Reply #2 on: February 14, 2017, 11:31:55 PM »
i was actually just about to but i decided to have another stab at it and it seems like everything (minus the more LED which I can live without) is working within reasonable ranges now. two things that i hadn't considered or noticed were 1) that the radio interference only happened when the input gain was absolutely cranked, which it really does not need to be, and 2) that there is a tremendous amount of output gain on tap, and when I level match the SLD with the rest of my board the remaining hum is around where it is with the rest of my pedals.

these are bugs i can live with because they don't affect the range of functionality i will be using.

thanks for reading!