Mains hum

Do me, and everyone else, a pleasure and killfile him.

Jeroen Belleman

The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:

And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:

And yet, the clueless John Doe troll has continued to post incorrectly formatted USENET articles that are devoid of content (latest example on Sun, 10 Apr 2022 17:54:27 -0000 (UTC) in message-id <t2v5kj$3av$ snipped-for-privacy@dont-email.me).

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Further, John Doe stated the following in message-id <svsh05$lbh$ snipped-for-privacy@dont-email.me posted Fri, 4 Mar 2022 08:01:09 -0000 (UTC):

Yet, since Wed, 5 Jan 2022 04:10:38 -0000 (UTC) John Doe's post ratio to USENET has been 56.8% of its posts contributing "nothing except insults" to USENET.

This posting is a public service announcement for any google groups readers who happen by to point out that the John Doe troll does not even follow the rules it uses to troll other posters.

jGjlGZ4zmCCO

Not so fast. A classic source of widespread hum fields is wiring errors or failures in the power wiring of the venue.

In the US, ring busses are not allowed, so out and back currents are close to one another, and their magnetic fields largely cancel. Unless someone reversed power neutral (white wire in the US) and safety ground (green wire). Which I have personally encountered.

War story: I've also encountered broken neutrals in 240 Vac split-phase (+120 - 0 - +120) power cables. I was attending a summer stock play (where my kid sister was acting) held outside on the grounds of a local school, as the light of day faded, I was looking idly at the stage lighting, and noticed that some lights wee too blue and other were too yellow. These lights are incandescent. Hmm. After the play, I approached the Director and asked him if he was having problems with things blowing out. Stunned look ... how did you know??? Told him of the too blue and too yellow lights, and that this implied a broken neutral. He was very interested. So we went along the main feed cable, opening Edison connectors. We quickly found one with the neutral completely un-connected. Director was *very* happy - he would have had to pay for all those brand dearly-departed new electronic dimmers. But it was the rental company's fault.

As for ring busses, which are allowed in Europe and I assume Australia, while if both rings are intact, magnetic fields will generally cancel, all it takes is a single ring break to force significant currents to take the long way around.

Yes, that's true these days.

I did find the patent I mentioned above. It's US 7,259,318 to Illich Chiliachki of California. The patent is now expired because later maintenance fees were not paid.

Joe Gwinn

Joe Gwinn wrote: ================ >

** So you say.

** Nor here - only in the UK AFAIK.

Such a buss feed a loop of AC outlets ( active and neutral) from both ends.

** Been true since the 1950s.

All the popular humbuckers ( Gibson, Fender and Asian clones) are metal cased.

...... Phil

Yes, unless there is a break somewhere. With luck, all the outlets will still work just fine, and nobody will be any the wiser. But the current will travel in a room-size or building-size loop, generating a pervasive magnetic field.

I did run into lots of exceptions.

Yes. I don't know when the transition happened, but it had to be gradual.

Joe Gwinn

Joe Gwinn snipped-for-privacy@comcast.net wrote in news: snipped-for-privacy@4ax.com:

I worked in a lab once where the PnP machine and the reflow oven benches were 90V to Earth ground. No hard current capacity that I could see, but still... They were clueless about ESD much less the introduction of stray line voltages. And it made for a very unpleasant tickle when one touched the wrong elements of the work area. I left that job pretty quickly. I do not like to work for idiots.

Phil Allison snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

Grounded metal case, as opposed to an isolated metal case. Can't leave that out.

mandag den 11. april 2022 kl. 01.27.40 UTC+2 skrev snipped-for-privacy@decadence.org:

likely a missing earth so caps the EMC filters form a capacitive divider to what should been earth

Joe Gwinn wrote: ================

** A rare event, only in the UK and the field is weak compared to typical transformers. > ** Seems you are accident prone.

** What "transition" was that ???

..... Phil