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Smashed Par Lamp


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Has any-one smashed a Par56/64 lately, I have and it left me a little surprised.


The last time I smashed a Par lamp was a Par56 about twenty years ago, when it smashed it revealed the linear filament - which gives the familiar letter box beam pattern - mounted on two 'legs' and this combined with the conical glass and lens were 'the lamp', without the glass envelope the filament would just burn out if energised.


It was a surprise then when I just dropped and smashed a Par64 to find that it contained a quartz halogen capsule lamp inide the outer conical glass and lens, similar to how a 50watt dichroic is made.


The internal lamp capsule was mounted inverted, with its base towards the lens, on two 'legs' obviously to place the filament in the correct focus position and it still operated without the outer glass envelope.


Perhaps others of you are aware of this change in construction it was just a surprise to me.

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They've been that way for a while. Perhaps its done like that so that the manufacturers can standardise on lamp/reflector assembly. Then all they need to do is attach different lenses depening on which type of lamp they want to make (CP60, CP61, etc)


Halogen lamps are generaly more efficient and/or longer lasting than non halogen types, they have therefore come into very general use for stage and similar lighting.


However a halogen lamp can not be made too large for a given wattage (certainly nothing like as big as a PAR or GLS)

This is because halogen lamps have a MINIMUM operating temperature for correct operation of the halogen cycle; if the bulb is too big, it wont get hot enough and therefore wont work correctly.

Therefore the only way to bring the benefits of halogen lighting to PAR lamps is to enclose a suitable halogen capsule within the outer envelope.


Mains voltage halogen lamps to replace GLS lamps are now available, they contain a mains voltage halogen capsule within an outer envelope similar in size to a GLS lamp.


Over cooling of halogen lamps can result in early failures, I found such a case in the reception area of an office building. Numerous downlights using 12 volt 100 watt halogen capsule lamps had been installed in a false ceiling. A badly designed ventilation system caused negative air pressure in the ceiling void, and therefore a huge air flow through the light fittings, right accross the lamp.


Theatre lanterns and similar equipment seldom over cool the lamps, though I met one case of a fan cooled colour changing lantern, I believe that the fan had been replaced with a much more powerful one, resulting in very short lamp life.


Early failure caused by overcooling often results in a dark, shiny coating on the inside of the failed lamp.

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Early failure caused by overcooling often results in a dark, shiny coating on the inside of the failed lamp.




That sounds very similar to an issue I have with some of my houselights at the moment. We generally get a short and inconsistant lamp life. There is a dark, sometimes shiny coating on the inside. Often the filament seams to break but only slighting so moving the lamp will cause the lamp to light again but often will blow properly at this point.

The units are in the roof with holes cut in to the ceiling to shine through - thoughts if this might be an over cooling issue?

We've eliminated over heating, bad wiring and bad bulb batch.



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If these are halogen capsule lamps, without an outer envelope then it may be overcooling.

Is there much air flow through the holes in the ceiling? If yes, then it might be worth reducing the air flow, either by use of fire resistant insulating material, or making an opening (covered by a grille) elswhere in the ceiling in order to divert the air flow away from the lamps.

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