Spitting sound at high hat with compact fluoresecent?

I have four high hats on a dimmer. I use them with the dimmer all the way up. When I put a nycompact fluorescent in certain one of the four, I hear a spitting sound. I do not hear the sound at the other high hats or if an incandescent bulb is used.
What problem should I be looking for?
Ken C
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Most of not all compact fluorescent bulbs cannot be used with a dimmer. Check the packaging the bulb came in to verify.
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Ken C wrote:

The problem of having a fluorescent on a dimmer switch. (Hint: You shouldn't do that).
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Ken C wrote:

You don't use CF with a dimmer.
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Joseph Meehan

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On Wed, 15 Feb 2006 12:30:43 GMT, "Joseph Meehan"

These are simple Levitton slide dimmers. Aren't thery just rheostats with the top setting the same as a closed circuit?
Also, why do I hear the spitting only when the CF is in the problem high hat but not from the same CF in the other three high hats? Why is one high hat different from the other three?
Lastly, I used a dimmable Philips CF in the past and it made the spitting sound too.
Ken C
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Ken C wrote:

Likely they are not rheostats. In any case it does not make any difference. Most CF's can not be safely dimmed. Trying to do so can cause a fire hazard. I suggest that if you need any florescent lamp dimmed that you make sure the entire fixture is designed to be dimmed and that you are using the approved dimmer for the job.

That I can't tell you. I might guess that there is a poor connection somewhere, but that would only be a guess. .

Were you using an approved dimmer?

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Ken C wrote:

This is a WAG, but you may just have marginal contact between that particular CF bulb's tip contact and the center contact inside the high hat socket The other bulbs you try in the same socket may have center contacts with slightly more projection, which smack down firmly on the socket's center contact when the bulb stops threading in.
Try this:
Make damn sure the power to that high hat is OFF (Switch the circuit breaker off if you're not sure.)
Use pliers to bend about 1/4" of the end of a straightened out (large) paper clip and use it as a "hook" to go into the socket, get behind the center contact, and pull out on it so that it bends and rises about 3/16" at its free end.
Household dimmers aren't really "rehostats", but you are correct in believing that when they are turned full up the ac waveform coming from them is practically indistinguishable from that controlled by a regular off-on mechanical switch.
HTH,
Jeff
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On Wed, 15 Feb 2006 11:53:42 -0500, Jeff Wisnia

Well, I couldn't pull up the center tab of the socket, but was able to put a solder bump on the lamp base. The solder is definitely making contact with the base pad, as is evidenced by the marking. Spitting is still there.
I pulled the switch and saw that it doesn't have external screw terminals. The wires appear to be pushed in and internally clamped down. I see no release buttons or the like. Is there a trick to getting the wires out of the switch or do I need to cut them?
Ken C
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Ken C wrote:

I've seen "one use" switches like that. Sometimes you can slide a very thin narrow blade like a watchmaker's screwdriver in alongside the wire while pulling and wiggling on the wire slightly and get the wire to work its way out.
If you can't get the wires out of the switch and have enough room and slack you could cut the wires a couple of inches from the switch, replace the switch with one wirenut and see if the frying goes away. If it does, replace the switch.
If it doesn't use two wirenuts or crimp splices to rejoin the wires to the switch and keep hunting.
Jeff
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wrote:

Dimmers are seldom rheostats (that would be inefficient). They use an electronic device (TRIAC) to control the output duty cycle. "full on" normally isn't that, it's something like 98% (I guess they're saving the expense of a switch to bypass the TRIAC). You may not be able to tell the difference in light output (from an incandescent bulb), but CF bulbs don't work properly with that odd waveform.
Note that the same thing applies to X10 lamp modules.

Maybe it's not quite as tolerant of odd waveforms as it should be. Does it require a special dimmer?

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Mark Lloyd
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