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I changed several halogen spotlight bulbs and after less than one hour, one exploded. See image.

enter image description here

It's an Osram Decostar, 35W. Although the bulb doesn't carry a "CE" mark, the box did.

We regularly have bulbs dying, so I suspect something might be wrong with our wiring, but I don't expect the bulb to explode. Usually they just die quietly.

My real question though is the root cause. What could be wrong with the electrics?

I checked the dimmer switch wiring and it is correct (with switched-live in L1 connector). Is there anything else I can check for?

Tim
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2 Answers2

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"One exploded after an hour" as indicated by @fixer1234 this is caused by finger oils or other contaminates on the lamp envelope itself (not the reflector). Its very important not to touch anything but the outer edge of the reflector.

Further what type of fixture is this bulb being used in? If the fixture is open faced situation such as this: enter image description here then the MR16CG must be used, (the CG stands for "Cover Glass") which has a self-contained lens. I mention this specifically because CG versions of the bulb tend to be harder to find and many people don't know when to use the CG version VS when the open face bulb is ok (i.e. enclosed fixtures).

"We regularly have bulbs dying" is likely a socket problem, replace the bi-pin socket the lamp plugs into. When heat is generated by the lamp pins this type of bulb will prematurely fail. (I know as hot as the lamp gets while burning this is hard to reason, but when the bi-pins generate heat from poor connection the result is premature failure.)

In the end, the best advice is to give is find an LED replacement that you are happy with. Unfortunately in many situations the MR16 halogen type of bulb is the hardest to replace with LED. It's very difficult to find LEDs that burn as brightly and with the colour clarity of the original - highly energy inefficient heat generating - halogen.

Community
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Tyson
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Halogen lamps are very sensitive to oils because of there high operating tempature. Oils from fingers cause a hot spot on the envelope and this hot spot can melt causing the lamp to explode. I have seen reflector types also have early failures on high power projectors. when removing the lamp from the package use a tissue so you never touch the lamp (don't use tissues with softners or creams). If you do touch the lamp some rubbing alcohol on a tissue can clean it off just make sure it is dry before turning on. The life on some of these lamps is only 200 or so hours when run at the rated voltage. I was surprised by this when checking a fixture out for a friend. I added a dimmer that had a upper limit control to reduce peak voltage and that almost doubled his lamp life.

Ed Beal
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