Mains Hum? 50 c/s ? Laminations on a step down transformer gone loose?
Had that problem on something years ago, took it out, squeezed the
laminations together in a vice ;-) and re varnished it :-)) Worked :-)

Mike
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It's nice to be important, but it's more important to be nice.
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Thanks for that pointer, Mike. I tried a different adapter and... no hum.
Brilliant! Thanks. Watch out for videos with sound, now.

Dave.

--
It is very strange, and very melancholy,
that the paucity of human pleasures
should persuade us ever to call hunting
one of them. (Samuel Johnson)