Electrical interference?


I've just plugged in a new desk lamp which sits on my computer desk - it has its own wall socket. When I switch it on or off, there's a loud 'pop' from the PC's speakers. How can I stop it? Need I bother? Thanks in advance for any advice.
Steve.
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Steve Bowyer wrote:

Bet it's a low power bulb, not an incandescent.
Andy
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Andy Champ wrote:

Strangely enough, I thought the exact opposite and would have bet on it being a halogen. The switch on "pop" could be due to the large inrush current into a cold lamp. THe switch off "pop" could be due to breaking an inductive circuit - a transformer between switch and wall socket.
However, probably nothing to get worried about. It might be stoppable, or at least reduced, by a ferrite core on the power lead.
--
Sue



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Palindrome wrote:

Ah, didn't think of that. I was thinking of the choke in a CFL. OK,
Bet it isn't a *conventional* incandescent!
Andy
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Hi First find out if your PC's feeding your speakers (ie they do not have a separate mains supply). If so you have potential problems as PC's don't like surges of any kind .(recommend you get a surge protection device either extinction lead with built in or stand alone ) Either way you need to identify what is causing the "pop" .(yes I know when you switch the lamp on ) the noise is interference which can be caused by the switch arcing,the lamp lighting or even a loose wire in the lamp or plug to name but 4. This causes interference which can be either transmitted through the mains cabling or radiated as a pulse which your speakers detect.(rather like when you touch the end of the phono plug and it hums).
Solutions vary depending on the type and cause try the following. Move the lamp away from the speakers and switch it on if still as loud most likely case mains born interference. A simple suppressor of filter should stop this.
If noise is softer then its more likely to be inductive (radiated pulse ) In this case a simple faraday loop** on the phono lead may cure it (or just relocate the lamp or main speaker)
The pop could damage the speakers eventually and if you have an expensive speakers then you should try and sort the problem.
"" find a ferite ring and loop the phoho lead through it 2 or 3 times .Try an old usb lead sometimes they have one. (ferite is like grey/black stone ) or if you have a mobile or camcorder sometimes they give you one in the box .(JVC did)
HTH
CJ
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