Overhead florescent light is now dimmer, why?

I have in the kitchen a pair of overhead light fixture. Each fixture has two florescent tubes and both fixtures are controlled by the same light switch.
Tonight one of them suddenly dimmed and remain about half as bright as the other one. No flickering, just half as bright. I thought the tubes may be going bad so I went and bought two new tubes - same wattage same brand. No difference. Still dimmed.
Any idea what could be the problem? Do I need a new light?
MC
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miamicuse wrote:

You could have a wiring problem, or a bad ballast. At least now you have two spare lamps.
You might try switching the ballast and see if the problem follows the ballast. Be careful and make really sure the power is off before doing any wiring work.
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Joseph Meehan

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I did recently tinker with another lamp next to the kitchen that has a different ligth switch. I replaced the original toggle switch with a dimmer type. I think I did it right, it works...
I have no idea if the kitchen overhead lights are connected to this other lamp in some way or not, is it possible one can affect the other? or when you say wiring you mean the wiring of the florescent lamps? If so then no, nothing has happened to it's wiring, other than hurricane Wilma we have a series of power up power down cycles.
Thanks,
MC
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MiamiCuse wrote:

The you could have a bad ground and that would be a wiring problem. You also could have a wiring problem inside the lamp, between the sockets and the ballast. I doubt if the other light is connected with this problem.
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Joseph Meehan

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be careful with powerful knowledge ahead at this link :)
http://www.repairfaq.org/sam/flamp.htm#pwf
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Does the dimmer fixture have only one tube lit? Are there starters in the fixture? If so, try replaceing them.
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Rich Greenberg Marietta, GA, USA richgr atsign panix.com + 1 770 321 6507
Eastern time. N6LRT I speak for myself & my dogs only. VM\'er since CP-67
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