My old light bulbs stopped working, so I bought 2 fluorescent U shape light bulbs as a replacement:

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The recommended power in the light fixture is 34W per unit but they only have 32W in stock. After installing the new lights, everything looks good and is brighter than before. However, I notice some pulsing coming from the lights, almost like a tremor. The light is solid white but somehow it's pulsing.

The lights have been on for at least 8 hours by now. Does anyone know what could be the cause of this issue? The old lights work fine no problem until they burnt out.


Probably the old ballast and new bulbs are not exactly compatible. Aside from the 32/34 W difference, are the new tubes perhaps 1/2" smaller in diameter than the old tubes? That would likely be a T8 tube replacing a T12 tube, and usually a ballast change is also needed to keep everything happy...

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  • Yes, the old tube was a T12, the new one has a smaller diameter and is a T8. Can a new ballast installed or do I need the help of an electrician? – Thierry Lam Mar 2 '14 at 0:01
  • That mostly depends on your comfort level with electrical projects. It's a DIY project for people who are OK with it, and an Electrician project for those that are not. Assess yourself and act accordingly. – Ecnerwal Mar 2 '14 at 0:04
  • I finally switched the ballast to a 32W, old one only supported 34/35W. Everything is working fine. – Thierry Lam Mar 10 '14 at 15:31

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