I have a strange problem with a fluorescent ceiling room light. There are four small fluorescent tubes. One day for no apparent reason they all just suddenly went out.

When I turned the light switch off and then back on, they turn on for a few seconds then went out again. I can repeat this any time.

Note that the two tubes on the left turn on instantly but the two on the right show a short (half-second?) delay at which time the orange glow of the filament inside the tube is visible.

How might I go about debugging this and eventually fixing it?

note: I live in Taiwan (120 V, 60 Hz), most electrical fixtures and appliances here are pretty standard. My apartment building isn't very old but watching the flickering of the light inside the switch I'm pretty sure that it's the old neon lamp type rather than an LED.

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    Try swapping the two pairs of bulbs, and say if that fixes it. Also tell us if there are any dark bands near the ends of any of the tubes. If not, then pull the lamps out, pop the covers off and look for any ballasts. we'll need photos of the label on the ballast. Commented Jan 29, 2020 at 7:37
  • @Harper-ReinstateMonica Thanks! Okay that will take a half-day or so to locate something safe to stand on.
    – uhoh
    Commented Jan 29, 2020 at 8:10
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    Modern ballast have safety’s that shut down the ballasts off if the tubes are drawing two much current.
    – Ed Beal
    Commented Jan 29, 2020 at 14:32
  • @EdBeal Ah! That makes sense. Yes the timing is so repeatable it does look just like an automatic shut-down. Okay I've figured out how to get up there so I'll play some musical chairs with the two slow-starting tubes and then try replacing them. If that doesn't solve it I'll look for the ballasts.
    – uhoh
    Commented Jan 30, 2020 at 0:21

1 Answer 1


As requested: modern electronic ballast have safety circuits that shut them down when the lamps are drawing two much current. Replacing weak lamps may solve the problem.

  • Indeed! I've removed the two slow-starting tubes and the other two are staying on. I'll update as soon as I can install two new tubes and confirm it works with all four. Thanks!
    – uhoh
    Commented Jan 30, 2020 at 14:16
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    I have learned over many bulb replacements it is practical to replace all the bulbs in a fixture when the first one burns out. It will cost a few dollars but saves a return trip. Commented Jan 30, 2020 at 15:53
  • Two new tubes still start slowly but everything stays on now. I'll look into replacing the ballast next time.
    – uhoh
    Commented Jan 31, 2020 at 23:37

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