Trouble light troubles

[letterman]

Now I know why they call them trouble lights.

This dont make sense. I plugged in one of my trouble lights, and immediately the bulb made a bright flash and burned out. I did not think much of it, I figured it was just a common dying bulb. I unplugged the cord and installed a brand new bulb. I plugged in the cord and immediately that bulb flashed and burned out. After cussing about the quality of light bulbs, I got yet another new bulb, and the same thing happened. Immediate burnout.

At this point, I unplugged the cord and measured the voltage at the outlet I was using. It measured 117V (normal). I plugged another trouble light in that same outlet and it worked fine. Then I plugged in several other power tools and stuff. All worked fine.

That's when I tossed this bad trouble light in the garbage.

However, I do not understand this. It's not getting 220V, so how/why did the bulbs keep burning out? (just on that cord).

[RBM]

The cord won't cause that to happen. I would check the voltage rating of the three bulbs that flashed. If it's not problem bulbs, I'd put a meter on the circuit and watch it for a while, as there could be an intermittent open neutral, causing high voltage

>

[Jim Elbrecht]

-snip-

The cord can't have the neutral side go open? Like right where the handle meets the cord? And where it stuck itself back together when the light was taken down from the workplace to the bench to be tested?

If it tested fine on the bench I'd sacrifice another bulb on a fresh circuit. If the bulb works I'd put the light/cord through a lot of gyrations before I suspected the old circuit.

Jim

[Jeff Wisnia]

Can you explain why you believe an open neutral in the cord will burn out a bulb?

I think you may have read posts about open neutrals in a main power feed and unbalanced loads causing high voltage on one phase and low voltage on the other.

Methinks you need to study that subject a bit more until you understand it.

Jeff

[dpb]

Jim Elbrecht wrote: ...

Agree w/ the latter...

I'd hypothesize there's a fault in the socket base that is causing a short when the bulb is inserted...

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[Jim Elbrecht]

I don't, necessarily. I didn't even think about it. But I didn't understand why RBM was having the OP test a circuit when Occam's razor would point at the cord first.

Jim

[Jeff Wisnia]

So, how will a "short" cause the BULB to immediately burn out?

I'd expect a short would more likely pop the breaker for that circuit, or if it wasn't a "hard short" it might cause localized heating probably accompanied by a bit of smoke/smell. And, as mentioned elsewhere on this thread, a poor contact or partial short might heat the bulb base enough to cause a "mechanical" bulb failure, but not "instantaneously".

I really can't think of anything which could go wrong with a trouble lamp cord which would cause an "immediate" failure of a bulb as soon as it's turned on.

I'd go with bad bulbs as the likely cause.

To check that, he OP might try taking a bulb from one of the other "working" trouble lights he mentioned he had and trying it in that bewitched unit.

Jeff

[dpb]

Or one of the supposed "bad" bulbs and put it in the working trouble light.

My thought would be a high current across the base is blasting them, but it's hypothetical. A poor vacuum seal on a batch would provide the symptom as well, certainly.

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[dpb]

[e-mail] wrote: ...

I'd do continuity checks on the cord, socket, etc., first as well as the visual inspection.

Obviously if have another in the batch of bulbs that failed, try it in another lamp/light first before the test of the problem one.

The only idea on the bulbs themselves I have would be a batch w/ an imperfect vacuum seal unless they are a really cheap Chinese import and/or mislabled.

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[Jerry - OHIO]

I have a trouble light that is used for automotive use ,with 12 volt bulbs just like 110 bulbs.Wife got my spare bulbs and blew six of them before she noticed they were the 12 volt ones. Now I keep my shop locked . Jerry

[The Daring Dufas]

I had a problem once where dingbats would come into the repair shop at my workplace and put regular disposable flashlight batteries in my NiCad charger. Made quite a mess.

TDD

[Jeff Wisnia]

A little bit OT, but I wonder how many folks here know that they still make and sell standard looking light bulbs with left hand threads?

It's an anti-pilferage thing. They were used aplenty on subway cars back when incandescent bulbs were the only practical lights abvailable.

I think the reason they are still being made is that the strings of lights used around construction sites are easy targets for "bulb snatchers" and using bulbs with left hand threads discourages that. (Confirmation please?)

Jeff (Who wonders if anyone ever sold "thread reversing" light bulb socket adaptors? )

[The Daring Dufas]

Back in the early 70's I worked for an electrical supplier and we sold a lot of left handed bulbs and pig tail sockets to construction companies. The thought of some miscreant trying to steal the bulb is kind of entertaining.

TDD

[Dave Martindale]

The solder is just an electrical connection. The gas seal is made by sealing a glass tube used to remove air from the bulb.

This isn't to say that a poor connection might not generate enough heat to soften glass and lose the seal - but it would have to melt glass, not just solder.

Dave

[lp13-30]

FWIW, bulbs made for ceiling fans will stand up to the rough service a drop light usually sees almost as well as the rough service bulbs made for drop lights, at a fraction of the price. I finally started using CFL's and find they last longer than rough service bulbs and don't put out the heat. We have had people at work burn carpets by setting drop ights down and forgetting about them, beside burning the crap out of arms, but the main thing is that one drop of sweat on a hot incand. will pop it immediately. One afternoon, me and a co-worker popped 4 or 5 in about a 20 minute period that way. Larry