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I got a cool lamp from a yard sale, its an arm mounted desk lamp that has a giant magnifying lens in the head and a circular fluorescent tube around it so its really nice for zooming in and illuminating whatever I place under it.

The downside is that it appears to be messing with the power delivery to every other electronic device connected to the mains in the moment when I turn it on. Some are more, others less affected but most annoyingly - it causes my stereo to black out every time I turn the lamp on. The stereo will come back on in like 10 seconds or so but still, can't be healthy.

What can I do to prevent this? Is it supposed to be happening or is the lamp broken somehow?

The lamps previous owner told me she had no issues with it, she was using it to zoom in on pimples in a beauty parlor haha.

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  • replace the tube with LEDs, or at least get a new starter/tube for it. From the description, it's probably ancient, which also means it's probably quality and worth salvaging. does it have two buttons for on and off?
    – dandavis
    Apr 29, 2019 at 21:50
  • @dandavis No just a regular flick switch. Why change the tube/starter though? The lamp itself works perfectly, also I checked out the tube, a new one would cost €30 which is twice as much as I paid for the lamp
    – user81993
    Apr 29, 2019 at 22:28
  • Why change the tube and starter? Because it's not working right. However I agree it's neither one.
    – Harper - Reinstate Monica
    Apr 30, 2019 at 13:43

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Fluorescent lamps are inherently electrically noisy, but a bad fluorescent tube or ballast can make the problem more severe. To reduce the radiated electromagnetic interference (RFI), try the following, listed from least- to most-expensive:

  • Try a different fluorescent tube.
  • Run the line cord near the fixture through a ferrite toroid choke.
  • Be sure the lamp is grounded (three-wire cord), which also helps safety.
  • Plug the lamp into an EMI (RFI) filter outlet.
  • If the above does not help, replace the "Circline" fluorescent tube with an LED device. Links are provided only as examples.

Note, though, that the electrical noise does no permanent harm to the radio or other appliances.

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Change it to an electronic ballast

There's nothing wrong with fluorescent lights inherently. However the early fluorescents relied on a design which was before electronics (and therefore, before anyone cared about line noise).

Fortunately, electronic ballasts came along in the 1990's, and they made things much better. It isn't hard to make an electronic ballast that has very little line noise and an excellent power factor, and also drives the fluorescent tube much closer to optimum conditions.

So, identify your tube type, identify the physical location of the ballast inside the lamp, and shop for a ballast that is a) rated for that tube, and b) physically fits (there are standards for fitment, so it will typically have screw holes in the same places).

If that proves difficult, then shop for an LED replacement "tube". Those come in 2 varieties: Plug-and-play (does not require ballast to be wired around, BUT depends on the ballast being there) which is stupid.... and Direct-wire, where you feed it mains power directly and the ballast is bypassed.

Mind you, I am biased; I think real fluorescent is a perfectly fine technology and I continue to invest in it. You may disagree when that tube burns out and you have to spend €30 to replace it! However if you don't see dark bands on the ends of the tube, that'll be a long time, especially with an electronic ballast.

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  • Note that some electronic ballasts (even for LED's!) switch at high spped, and the resulting square waves have harmonics well into the FM broadcast bands. There are two LED lamps in my bedroom that increase noise on an FM radio across the room; so I needed to add RF chokes to the lamps' line cords to be able to listen to DX.
    – DrMoishe Pippik
    May 1, 2019 at 17:57
  • @DrMoishePippik If they are at all competent in their jobs, they suppress that EMI/RFI in the usual ways. This is required to get an FCC cert, but lots of cheap Cheese junk makers don't bother because they are just faking the FCC label. That junkstream winds up with a lot of private labels on it.
    – Harper - Reinstate Monica
    May 2, 2019 at 14:58

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