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I have a 3-bulb fixture on a 3yo dimmer. It seems -- and this is really impossible to prove -- that the buzzing/singing of the dimmed bulbs has gotten worse over time. It doesn't really make sense to me that the circuitry would get worse over time though I suppose the heat dissipated by the power components could make them operate more poorly. Before I replace the dimmer just to see if a new one makes the bulbs sing less, I thought I'd ask if any one could support or refute the idea that old dimmers make bulbs noisier.

Chris Nelson
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  • I'm assuming we are talking about conventional dimmers and incandescent bulbs here. Have you tried changing bulbs? Heavy duty or "long life" bulbs have slightly heavier filaments and supports, they tend to make less noise. I'd believe filaments get louder before I'd believe the dimmer is causing the bulbs to be louder, though I'm not totally discounting the latter. But I'd expect the dimmer cause to take much longer than 3 years. – bcworkz Feb 24 '14 at 22:32

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TRIACs do tend to wear out. As they age, the waveform becomes more jagged. Here is what a good TRIAC should do to the waveform when 50% dimmed:

enter image description here

Here is what a failing TRIAC might look like:

enter image description here

(That is actually the current of a CFL: I couldn't find a failing TRIAC waveform.)

If it is failing, TRIACs seem to fail pretty quickly and enter an intermediate poorly-performing state for only a few hours or days.

You could unscrew one or two bulbs in the fixture and see if that improves the situation to isolate whether it is the bulbs or the dimmer.

For more details about dimmers, see this.

wallyk
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