1984 Mazda 500T52 (500 W / 24 V)

In the early days of the Tungsten-halogen lamp technology, in the 1960s, the cost of manufacturing large quartz lamps was still quite high. As a result, a number of medium- and high-wattage halogen lamps intended for special lighting applications were simply made with aluminosilicate glass, which was more suitable for small-series production runs, especially since traditional lamp making techniques could be used. This practice continued until the 1990s, when the production of quartz lamps had developed to a point where it became more economical to end the use of softer glass materials in these lamps.

The 500 W Mazda lamp presented here is one of those earlier special halogen sources built with an aluminosilicate glass bulb, manufactured by Philips for the French market. This particular model has a very compact coiled-coil tungsten filament designed to run on 24 V power for maximum luminance and efficacy, suitable for precision floodlighting in stage and studio applications. The source’s performances are maximized thanks to a filament operating above 3000 K, which brings the lumen output to 13 klm, corresponding to a 26 lm/W efficacy. However, such an operation also reduces the lamp service life to 100 h only.

The lamp is fitted with a P40s prefocus base in order to precisely align its filament with the projector’s optical system. The lower part of the tubular bulb is painted black so as to raise the temperature there and ensure a high enough bromine vapor pressure for an optimum tungsten-halogen cycle. Such measure is necessary since this lamp is rated for a vertical base-down ±135° operation, which could definitely result in a too low cold-spot temperature.