I just replaced the fluorescent lights in my kitchen - two of the 40w
type, about 47" long - when the old ones would no longer activate.
After putting in the new ones, I find that after about 30 secs from
being turned on, the lights begin this rapid shimmering or pulsing.
Hard on the eyes and annoying.
The old ones were fine before they died, didn't exhibit this behavior.
Does this sound like some problem with the lights themselves or some
problem with the light fixture that perhaps didn't show up with old
Could also be impurities inside the lamps that get caught in the arc. If
you see what appears to be swirling or wavering of the light inside the lamp
and not a rapid periodic flicker at some fixed frequency, then the problem
will likely take care of itself after a few burning hours. Some people take
the lamp out of the socket, switch it end-for-end and then claim that solves
the problem. I don't think so; but it won't hurt anything either.
The phenomenon is rare these days with the quality control that the major
manufacturers have in place; but I see it with a few new lamps once or twice
The best source I've found is Don Klipstein's
Try this page and scroll down to "Troubleshooting Flourescents":
You might want to try a different brand of bulb before doing anything else.
If the lamps (bulbs) are swirling or shimmering, I would let them break
in before spending money and time on replacements.
Also, once broken in, they may not behave until after being turned off
and back on again - I have seen that happen.
If you do get new lamps and the lamps are T12 (1.5 inch diameter), see
if the cranky ones are 34 watt, 35 watt or otherwise "energy saver". In
my experience, these are more likely to be "cranky" than true 40 watters
when the temperature or the ballast is marginal.
Some "residential grade" ballasts underpower the lamps significantly,
and lamps that get cranky more easily can do so with such ballasts.
True 40-watters are now supposed to only be available in specialty
colors, higher color rendering index versions of white, or in packaging
saying "residential use only". A higher color rendering index one with
uncompromised light output is Philips Ultralume 4100.
- Don Klipstein ( firstname.lastname@example.org)
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