Okay, here's the deal: When I moved into this place, I got a couple of
standing, torchiere (sp) halogen lamps. 500 watts. Pretty damned bright.
        As soon as I started using them, the metal screens over the bulbs
(to keep bugs from getting in, or you from touching it, or something) started 
smoking. So I took them off. Then one stopped working, and when I looked
closely, I noticed that the insulation on the wires was scorched to hell, 
and the pseudo-ceramic end caps on the bulb broke off, and it generally is
a piece of crap and not designed for high heat. Which is silly, because a 
500w halogen bulb gets DAMNED hot. 
        I only run these at 1/2 power or so, but it burned out the mountings.
        Anyway, the other one went soon after, and I tried my hand at fixing 
them. 
        They both work, but...
        I fixed them by using whatever I had (a screw in one, I think a nail in
the problem one) as the end contacts for the bulbs. This worked with the 
screw, but the other one won't stop buzzing. This is a result of using the
dimmer to make it 1/2 power - the dimmer, of course, simply cycles the 
electricity on and off. Somehow this makes it buzz.

        My question is, what specific technical thing makes it buzz, and how 
can I stop it? It buzzes a lot when an exposed bit of wire with power in it 
is touching other metal, and buzzes a bit no matter what. 

        I can't really use the one at full power - 500w gets expensive, and
will comfortably light the neighborhood.

        If anyone knows where to get actual official mounts for these, so 
they aren't just jerry-rigged and liable to spark and explode, let me know,
please. The bulbs are about 5" long, pencil-thick, with contacts at each end.
I got 'em working, but...

        (spark, pop)

16 responses total.

You probably don't want to run them at half power.  Chances are they'll
burn out sooner.  You might want to see if you can't get smaller bulbs
instead.  It may be buzzing because the filament is getting
slightly hotter and cooler as the current flows, switches direction,
turns off, then flows again.  The dimmer would make this worse,
by letting full current flow for only a bit, then turning all the
current off.
If you can find a DC power supply for the bulbs, that should
fix the problem.  A variable voltage switching power supply
would work pretty well at this.  If you always want to run
both at half power, hooking them up in series might well also
work (of course, at the potential expense of bulb life.)

500 watts?  Yikes, that must really get hot.  When I bought my
first halogen light I was quite surprised at how much heat a 50
watt bulb bulb emitted and when I read the instructions, warning
not to ever touch the bare bulb even when it was off and cool
otherwise it may be prone to explode, well I wondered whether the
whole concept was worth the danger.

Since then we've aed aquired two more halogen lamps - the light
is very pleasant for reading and fine work.  But we made very certain
they all had protective shields over the bulbs along with obvious
ventilation.  An awful lot of these lamps don't have one or the other
of these safeties.

So, I guess I haven't really helped you with your question, and
in spite of my hesitation on suggesting anything might "explode"
please be careful here.  That bulb must get extremely hot and it
sounds like in working with it you might have left some finger-
prints behind and this is what could cause the sucker to go
atomic (or so I've been told).

We've got one of those torchiere 500 watt guys.  First bulb burned out 
in about a month, 2nd bulb has lasted about 2 years, so far.

I was aware fingerprints would shorten the life of the bulb, but 
I didn't think they'd explode...
Hmmn...
I've been handling them with protection (yeah, I always wear a condom).

I think the snapping and popping is a little more bothersome than the
buzzing - The one doesn't buzz. They only seem to buzz when they're loosely
seated, or something.

Right now, the bad one has the bulb just touching the wire on the one side, 
which can't be too good.

   >=========<
   |         |       - normal, with the === being the bulb

   >=========%    <---- just wire
   |         &

        POW!

Touching the glass will slightly etch the glass and leave behind oils.
Whe the bulb is turned on, it gets real hot, causing severe stress in
the glass. Oil and etching will cause concentration of this stress and
snap, it breaks.  The bulbs need to run hot for the halogen cycle to
work.  If they are run at partial power, metal evavorated off the filliment
will condense on the glass instead of back on the filliment because the
glass is too cool.  This leads to blackening of the glass and premature
failure of the lamp because the filliment burns through.  

The buzzing you mention is may well be caused by the dimmer.  Dimmers
chop up the normal sine wave power going to your lamps, causing all 
kinds of harmonics to be produced in the bulds filliment.  

The buzzing is the dimmer- the snapping and popping is the poor contact.
My mother has insisted she provide me with new lamps for christmas, in the 
interest of safety.

I saw some 75w halogen bulbs at meijers the other day.  Turns out it's
actually a double layer deal -- a tiny inner bulb (which is going to get
real hot), and a more or less normal sized outer shell.  It still warns
you not to leave fingerprints on the glass, but I suspect it's not
nearly the big deal it would be if it were just the single layer of
glass.  Auto headlights seem to work about the same way -- you can get
either very tiny single layer bulbs, which you need to be real careful
about, or full sized deals, which are probably no more fragile than
ordinary sealed beams.

The 75w bulb was $10.  Even though it lasts 7000 hr, I have a feeling
it's still a losing proposition compared to a normal lightbulb, unless
you really really hate replacing the things.  They didn't say how much
light it produced, which was a curious omission.  But they did have
plenty of warnings about not using it outdoors or in other hostile
environments.

If you take a close look at those full size auto halogen headlamps,
you will find that they have a much smaller bulb inside which can not
be removed.  This is the actual halogen lamp.  The silica envelopes
on halogen bulbs must run very hot.  You can probbaly reduce the 
voltage to the bulb by about 10% and increase its life significantly.
Much more than that and the life span will again decrease.

The reason I prefer halogen bulbs over incandescent is that the halogens
give "white" light, and incandescents (hmmn...am I spelling this wrong?)
give more of a yellow light. 
Nothing that's 75w is going to do me any good, though, I hate little dim 
lights.
75 incan overheads worked okay...
The 300w halogen bulb I just picked up a while ago didn't cost too much 
more than that 75w. 

Watts is not necessarily a measure of the amount of light you'll get.

True enough. Halogens seem to give a little more than incandescents, and
xenons blow everyone out of the water.
And if it's DC powered, who knows.

If it's DC powered it just burns out a bit quicker.  (Cause  the current
is always goin the same direction.)

That dosn't make any sense, why would a light burn out quicker if it's 
powered by DC current rather than AC (assuming it is taking the same amount
of power in each case)?

Has something to do with the migration of tungston (or whatever) atoms
in the direction of current flow.  The filliment thins on one side and
thickens on the other if the current always flows in the same direction.
Sooner or later, it gets too thin and *flash*.  Lamps also usually burn
out when they are first turned on, not while they are burning.

bad contacts can make it buzz too, since bad contacts have more resistance,
and more resistance causes heat production synchron to the current flowing
thru.  Since the current jumps from 0 to max in a matter of few hundert micro
seconds, also the heat produced there and temperature jumps. As a result
the metal around the contact expands 'instantly' sending a mechanical wave
thru the metal connections, which can be heard as buzzing.

There you go.

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