Donald L Burdette wrote: > > Glenville T. Sawyer wrote: > > >However, having been in the Theatre lighting / Electrics industry for a > few > >years I would advise AGAINST dimming Low volt' Halogens. > > unless a halogen lamp is run at its (normal) - preferred > >operating temperature, you WILL find that the life of the globe / lamp > is > > reduced by quite a dramatic amount, these lamps seem ( from Practical > > experience ) to prefer full voltage - to achieve maximum lifetime > operation > > within design parameters. > > Are you sure the large high-voltage globes you used in theater work have > the same charactistics as the miniature low voltage ones being talked > about here? > > One reason I ask is that our local home goods/hardware store sells low > voltage halogen kits with dimmers. Are they selling a product that > damages itself, or is something different about them? I have no idea > whether they are or not, does anyone out there know? One thing I was > able to see from the packaging is that the dimmer goes between the mains > and the transformer. I believe the lamp life is considerably reduced by low power running. Now, I'm no expert, but I believe what happens is....... As the lamp is operating, small parts of the fillament vaporise and condense on the quartz envelope (These are not glass), under low power use, this metal stays there(this is what causes blackening of the lamp), where as under full power running, the envelope gets heated enough for the metal to evaporate back into the gas. The more metal in the gas, the less gets evaporated from the fillament. (Like a saturated solution almost). Also, as the lamp cools a proportion of the metal condenses on the envelope and a proportion back on the fillament. That was not a very clear explanationm however I hope you get what I meant. -- ----------------------------------- Brad Campbell Technical Manager Seme Electrical Engineering Co 59 Collingwood St Osborne Park 6017 Western Australia Ph :-+61 8 9445 2577 Fax :-+61 8 9244 1327 Email :- brad@seme.com.au /"\ \ / X ASCII RIBBON CAMPAIGN / \ AGAINST HTML MAIL