Re: 2235 power supply noise

Ed Breya
 

Tom, you can probably rig something up to see the sounds with a plastic tube for probing around the circuits, with a small electret or whatever type microphone shoved into the other end of the tube, The tube will safely convey some of the sound away from the hot circuits and strong electrical interference, to the mic, where it can be amplified up to observe. It may also need a bunch of low-pass filtering and shielding to cut out the stuff above audio. The electrial interference may be quite strong even some distance away - maybe stronger than the mic signal.

The kind of mics I picture are those little Al cylinder types that are in almost everything that has voice/sound input - especially phones. It's the same setup as the old mechanic's trick, except that instead of the tube going to your ear, it goes to a mic. It definitely won't be precise, but may be OK for locating stuff, and relative measurements.

You can also build or get ultrasonic receivers/downconverters to see/hear the sound above audio, emanating from SMPSs and other stuff.

Ed

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