Re: Halogen projector bulbs

[P3D Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

Linda writes

>I have a TDC 716 projector, and wondered whether it would be advisable
>to replace the bulbs with halogen ones, when the current 750W bulbs go
>if not before.  Dalia apparently sells a 500W bulb (13,000 lumens, 100
>hour life) to replace the CZX 500 normally used in the TDC 116 and other
>projectors.

Good question and would like to know about this regarding the TDC 116,
anyone know in either case?

>Nothing mentioned for the TDC 716 (which normally uses the
>DDB 750) in the catalog I have. Does the 500W halogen just improve light
>output of a 116 to be to be more comparable to the 716? I hear that the
>projector is supposed to run cooler, although I don't understand why
>this would be the case with comparable wattages to generate the heat.

Actually I think why they mention it runs cooler is because the lamp
is run hotter! What I mean by this seemingly contradiction is by
running the lamp hotter, more visible light is produced and less 
infrared heat. Thus the projector runs cooler. The same wattage is
consumed but more efficiently since less is lost to heat.

An analogy to illustrate this is a room lamp dimmer. If it is set
at a low setting, the lamp glows red and more infrared (heat) is 
generated and not much visible light. If the dimmer setting is set
higher, the temperature of the filament is "hotter" and the lamp
glows white and less heat is generated relative to the visible light.

It is true the lamp is running at a higher wattage at the higher
setting but the important thing to keep in mind is the brightness
relative to the infrared. Keeping this in mind, halogen lamps
are operated at higher temperatures compared to similiar wattage
regular tungsten lamps, and consequently burn brigher.

>Also, I thought there was a recent posting that mentioned using  250W
>halogen bulbs. Does anyone know how the light output of the 500W halogen
>compares to the old 750W? Are there any disadvantages to "halogenizing"?
>If 250W halogens would be suitable, is there a good source for them?

As mentioned, yes there is an advantage to "halogenizing", since they
normally are run at higher temperatures. The 250W bulbs, most likely
are of a different package with a more compact coil and more efficient
reflector incorporated in the bulb housing. This improves efficiency 
drastically since alot less light is lost in the rear and sides of the
lamp. I would also like to know if there is anything readily available
on the commercial market for 50's type 3D projectors. I think I saw a
project describing using 250W bulbs a long time ago, but the projector
had to be modified if I remember correctly.

Gabriel


------------------------------