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Old 03-12-2019, 01:28 AM   #16
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Re: Hum Hum Hum!

Quote:
Originally Posted by Mark_ View Post
Then again this is a good reason not to earth to your plumbing.
>>>I've connected an old speaker wire between a lug on the PC for attaching some sort of locking mechanism and the radiator<<<

Oops!

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Old 03-12-2019, 03:00 AM   #17
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Re: Hum Hum Hum!

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Originally Posted by Uncle Gizmo View Post
>>>I've connected an old speaker wire between a lug on the PC for attaching some sort of locking mechanism and the radiator<<<

Oops!
I think (but am not qualified) that it's part of build regulations to have your plumbing earthed in the UK...
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Old 03-12-2019, 03:03 AM   #18
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Re: Hum Hum Hum!

The distinct tingle is a probably a result of the earthing being poor, allowing a potential difference (voltage) to build up.

In theory once earthed the problem will dissipate (pun intended)

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Old 03-12-2019, 02:27 PM   #19
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Re: Hum Hum Hum!

My guess is that the power supply is not properly grounded (or the motherboard has a bad ground connection). Hums in speaker systems a lot of times(back in the day) were caused by a floating ground.
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Old 03-12-2019, 03:00 PM   #20
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Re: Hum Hum Hum!

Quote:
Originally Posted by Uncle Gizmo View Post
I've connected an old speaker wire between a lug on the PC for attaching some sort of locking mechanism and the radiator.
There is something wrong with the Earth connection from you power point, the lead or the computer power supply.

Quote:
As I was preparing the end of the copper wire, I had attached one end to the PC, I was holding the other end ready to attach it to the radiator when I got the distinct tingle from it. In other words the PC case has some sort of voltage associated with it.
There are capacitors between the live and chassis, and the neutral and chassis designed to bypass high frequency interference to ground. If the chassis is not earthed the bypass capacitors will put small but detectible voltage onto the chassis.

Wherever the earthing has failed, you need to get this fixed.
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Old 03-12-2019, 03:03 PM   #21
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Re: Hum Hum Hum!

I'd also open the case and make sure nothing is loose and touching the case. Stray live connection can cause immense problems.
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Old 03-12-2019, 03:26 PM   #22
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Re: Hum Hum Hum!

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Originally Posted by Mark_ View Post
I'd also open the case and make sure nothing is loose and touching the case. Stray live connection can cause immense problems.
If that were the problem there would be more than a tingle on the case.

I used to work as a electrical/electronics tech in the renewable energy industry and have first hand experience with bypass capacitors putting small voltages onto unearthed equipment.

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Old 05-01-2019, 02:47 PM   #23
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Re: Hum Hum Hum!

Quote:
I believe I need to refrain from asking what you've chosen for your seat...
Cotton-blend pants on naugahyde seats leads to static buildup. In which case a poor ground will allow you to discharge it in the MOST unexpected ways. But sorry, no cameras were rolling at the time.
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Old 05-01-2019, 03:33 PM   #24
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Re: Hum Hum Hum!

maybe put a voltmeter between the end of the wire and the radiator?
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Old 05-01-2019, 04:21 PM   #25
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Re: Hum Hum Hum!

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maybe put a voltmeter between the end of the wire and the radiator?
Won't that knacker the volt meter?

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Old 05-01-2019, 04:50 PM   #26
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Re: Hum Hum Hum!

No, not unless you SEVERELY over load it, which I doubt you could. While I know of one case where one blew up on somebody, that was from putting several thousands of volts into one that shouldn't have had more than about 300 impressed on it. I was a diesel mechanic in a previous work life and did quite well on the electrical side of things, especially on exams. What you'd be doing is checking the potential between the pc case and some ground, which isn't really any different than if you put across a battery (DC) or across your household electrical outlet. The meter won't conduct current unless you've got it set to measure current, so don't do that if it's a multi-meter. Otherwise, as I said, you're just measuring potential. If you get 50V, that's how much is leaking across that wire. NOTE 30VAC is enough to kill you, so I suggest you don't screw around with this issue. If you've got leakage to ground from a power supply or something on that pc case you are playing with danger. Usually these things don't get better - they get worse.
EDIT
Do I have to point out that you don't hold the metal prongs of the meter leads in your hands?? It should go without saying that you need to be insulated, but assumptions can be dangerous.
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Old 05-02-2019, 12:13 AM   #27
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Re: Hum Hum Hum!

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I was a diesel mechanic in a previous work life
Well I'm blowed! Same here! I worked on lorries for several years (for The Americans, lorries is an English term for a lorry? In America that would be a truck! Possibly!)

I was also pretty good at sussing out the electrical faults. Mind you I had the opportunity to look under a HGV bonnet recently and there was this big box under there, I think it said something like danger 7000 volts! It was something to do with the electronic diesel injection system. Made me realise that I probably shouldn't consider tinkering with someone's lorry, not without getting a refresher on health and safety!

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