Being rather new to diyaudio forgive me if this the wrong section...
I was wondering if it's possible to check a PCB for ground loops with the use for an oscilloscope (or any other test equipment) and if so, how.
Thanks
I was wondering if it's possible to check a PCB for ground loops with the use for an oscilloscope (or any other test equipment) and if so, how.
Thanks
you need a local magnetic hum source, for example a tape head demagnetisation tool. then you can probe around and listyen for hum
Thank you basreflex. Do you know if there's any off the self or diy project that could do this as I'm not totally sure how to do it myself?
not really, there is another source of hum wich is sometimes incorrectly called groundloop, and that is current running through a coniductor that is also part of a signal loop, for example a feedback path;
than can be found by injecting a current between 2 ground connections, for example the input and output ground of an amplifier system, and then listen or measure the resulting hum. mixing panels alwasy are problematic as the summing amplifier has a large gain for any voltage appearing in a ground conductor.
than can be found by injecting a current between 2 ground connections, for example the input and output ground of an amplifier system, and then listen or measure the resulting hum. mixing panels alwasy are problematic as the summing amplifier has a large gain for any voltage appearing in a ground conductor.
The reason I'm asking is because I have a PCB where I get a bit of hum at 50Hz and I'd like to trace where it's coming from. I tried the same PCB with a different PS but the result was very similar (actually a bit higher hum) so I think it might be the PCB itself that cause this hum.
It is not audible, it's pretty low but it is there indeed and I'd like to eliminate it.
It is not audible, it's pretty low but it is there indeed and I'd like to eliminate it.
first you have to establsih what is the mechanism of entering the hum. put it in a metal box connect to gnd, does it still hum ?
then it's magnetic, if it's gone it's electrostatic , capacitively coupled. then screening helps.
then it's magnetic, if it's gone it's electrostatic , capacitively coupled. then screening helps.
Can you post the schematic, and a photo? However, a 50Hz hum is more likely to be inductive coupling, rather than galvanic coupling,
unless you use a half wave rectifier.
Unfortunately I don't have a schematic. It's some unkown diy inductor eq that i got for cheap. Not much info. as I said, it's not a big issue, I can leave with that since it's not really audible.
My question about tracing ground loops on PCBs is mostly for academic reasons and also because I design some PCBs from time to time so it would be nice to know.
My question about tracing ground loops on PCBs is mostly for academic reasons and also because I design some PCBs from time to time so it would be nice to know.
Here is an example of such a tool:
https://www.diyaudio.com/community/...r-hum-problems-the-humboy.378178/post-6815018
It does lot of other things too, but magnetic hum detection is one of its most important (and useful) features