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Lightbulb Base Failure

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Not audio, but lightbulbs are tubes, right?

Last night I heard a nasty growling sound from a light, as it failed.

Upon inspection, this is what I found (See pics).

This light (it's actually a heater bulb, for a bird), has been on 24/7 for probably 10 years.
I'm wondering if the damage I'm seeing happened all at once, when the bulb/socket failed. Or if maybe metal was creeping, and eventually created a short.

Basically, on pic one, in the circle is a very fine coating of metal, on the glass insulator of the bulb socket. It is partially conductive. I measure about 4k ohms across a couple mm of the substance.

But, pic two has some amazing metal migration.. (This, I'm pretty sure happened all at once when the bulb failed) The brass of the bulb socket is coating the glass insulator. Along the edges of the metal (which is now on the insulator), It's fully conductive. The middle of that area is coated in glass, and not conductive, where the ceramic bulb socket must have vaporized too, and then been deposited as glass on top of the brass, which was deposited onto the glass insulator.

Crazy!!
 

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Not metal migration, arc from center contact to socket center contact resulted in increased resistance. This resulted in more arcing until it melted the center conductor and the arc blew it away from the center point.

Look at the socket for more damage.

Replace the whole shebang.
 
The socket is completely empty at the base!
There are a few rows of threads towards the top (builb) end.
But the bottom of the threads, as well as the center 'hot' conductor are completely gone!

But also, it's definitely the brass threads that somehow got blown UP onto the glass insulator.. (bulb was facing down, the base, at the top). I don't think it was an arc to the center conductor melting it down onto the insulator.. In pic two, that's not stuff on the brass threads.. those threads are missing, and the ceramic under them is melted!
That part seems strange to me.
Otherwise, I think you're probably right about what happened. Maybe the arc started at the threads and quickly sparked upwards, taking the metal w/ it...
 
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I once burned most of the end off a Craftsman flat blade screwdriver with 120AC. Since I was doing something that I should not have been, and it was the boss's screwdriver, I stopped at Sears to purchase a new one. The clerk looked at it, said "lifetime warranty", and handed me a new one! :p
 
I once burned most of the end off a Craftsman flat blade screwdriver with 120AC

I blew about 1/4 off the end of one when I slipped in the breaker box and sparked one of the 120 VAC buss bars to the chassis. Sears would not replace it since I had subjected it to abnormal abuse.

I have had some rather weird failures in light fixtures where the bulb is facing downward. The base gets exceedingly hot. Heat plus Florida humidity plus copper creates the green growth which does conduct electricity. Red Florida fire ants conduct electricity too due to their tannic acid content. The bird, or any live creature exhales humidity, so you probably have similar conditions.

We have had two CFL's fail, one quite catastrophically in the garage ceiling fixture. One did the arc, flame, smoke and bang thing when the green growth grew on the PC board eventually creating a short, which created an arc, which carbonized the cheap phenolic board, which exploded in flame, blowing the little wire over to the base contact in half. All of this happened without blowing the breaker. There was no fuse or other fail safe mechanism inside the base.

The second CFL was a Chinese made GE. It started making a rude buzzing sound as the light dimmed and smoke came out of it after a power surge. Sherri turned it off. Autopsy revealed that this one used 1/4 watt resistor for the fuse. It "blew" from the power surge, and then arced across until Sherri turned it off.

We went back to incandescents for the garage for this reason.
 
Not audio, but lightbulbs are tubes, right?

Yep, uniodes.

Typical arc-over failure. The resistance of the filament won't allow enough current to open a fuse or breaker, but an arc can get extremely hot even if the current is limited to an amp or so. Not hot enough to weld steel, but hot enough to melt brass.

As for CFLs, I hate those things. They're electrically noisy and they're not as environmentally friendly as good ol' fashioned bulbs. I'd rather have tungsten in the local landfill than mercury. Why worry about Hg-vapour diodes when your house is filled with CFLs? That's just plain goofy.
 
CFLs, I hate those things.

Not my favorite either, but the typical Chinese made incandescent light bulb lasts a few months of nightly use. Sometimes only a few weeks especially in inverted operation because the base gets cooked.

The CFL's were supposed to last "years". I put CFL's in the hard to change locations like the front porch and garage ceiling. They blew just about as often as regular incandescents, especially during summer lightning season. I switched back to incandescent.

I just started to move in to a new house, and we will use a mix of incandescent and LED there. We will see how the failure rate of those $3 10 watt LED's from MPJA goes. I got a box full for the new Tubelab basement workshop.
 
I do actually have a carbon filament light bulb that I turn on every now and again for mood lighting. It burns 60 W according to the label and emits a few photons every now and then, if it feels like it.

For actual lighting, I'm a big fan of LEDs. I do have a couple of CFLs around, but don't care for the light they put out or for the warm-up time. Once they burn out, they'll be replaced with LEDs.

With a decent quality LED bulb, the quality of the light is as good as any incandescent bulb and thanks to the lower energy use, they pay for themselves within a year.

~Tom
 
I have about 40 Cree LED bulbs installed in my house over the last year or two. Zero failures. Made in North Carolina. Fork Chinese stuff, wondering when and how it will fail.

My CFL experience is as for others. They don't last. And if you are a good person, you have the hassle of proper recycling.

Waiting for Cree to release candelabra bulbs, then my conversion to LED will be complete.

Ain't no good for keeping birds warm, though. 100 Watt equivalent LEDs are only warm to the touch.
 
I've made a bunch of LED fixtures for my house too! I generally use BridgeLux emitters, build a CCS for them, and then the complex part is designing the fixture.. These are big flat emitter chips, and don't exactly replace a light bulb.

Plus, LED's finally have up near 100CRI, so they look good! I feel bad for those who get the cheap blue-white fixtures.. But the new batch of emitters, which will certainly make it in to commercial fixtures soon enough, really look great.. Can't tell it's not incandescent.

Pics are my most recent lights, from the fall.. They were built to over-winter plants, but the light fixtures will find a permanent place somewhere in my home.
 

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+100!

I have about 40 Cree LED bulbs installed in my house over the last year or two. Zero failures. Made in North Carolina. Fork Chinese stuff, wondering when and how it will fail.

My CFL experience is as for others. They don't last. And if you are a good person, you have the hassle of proper recycling.

Waiting for Cree to release candelabra bulbs, then my conversion to LED will be complete.

Ain't no good for keeping birds warm, though. 100 Watt equivalent LEDs are only warm to the touch.
 
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