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Halogen Theatre Spotlight T/15 |
The first theatre lamps were incandescent types, and during the 1970-1990s those were entirely superseded by halogen lamps offering 100% lumen maintenance and 2x-4x longer life. However they also cost far more, and in the theatre business it took several years before they could be made competitively enough to finally usurp the incandescents.
Halogen projection lamps can only be made with quartz of the finest chemical and optical purity. In the early days this was extremely expensive, especially in the large diameters needed for high wattage lamps. This lamp shows one of the most important steps in solving this problem, following the invention of Thorn Lighting's Alex Halberstadt. Thorn was first to achieve the large diameters by purchasing lower cost small-diameter quartz, and inflating this to a larger diameter only around the filament so as to prevent overheating at that critical location. The concept was patented and the resulting cost advantage made Thorn a global leader studio and theatre halogen business. The T/15 model shown here was introduced in 1972 to replace the earlier incandescent T/6 - a type which was operated base-up. This required an unusually long neck to prevent overheatng of the thermally-sensitive quartz-to-metal end seals.
| Manufacturer: | Thorn Electrical Industries | |
| Lamp Power: | 1000 Watts | |
| Lamp Voltage: | 220 Volts | |
| Lamp Current: | 4.55 Amperes | |
| Cap Type: | P28s | Ceramic |
| Bulb Type: | BT-35 | BT-11 in eighths/inch |
| Bulb Finish: | Clear | Quartz |
| Filament Type: | C-13 Monoplane Grid | h=17.5mm w=18.0mm |
| Atmosphere: | Nitrogen | Bromophosphonitrile |
| Luminous Flux: | 23,000 lumens | |
| Luminous Efficacy: | 23.0 lm/W | |
| Luminous Intensity: | N/A | |
| Beam Distribution: | N/A | |
| Colour Temperature & CRI: | CCT: 3050K | Ra: 100 |
| Chromaticity Co-ordinates: | CCx: 0.434 | CCy: 0.403 |
| Lifetime: | 750 hours | |
| Burning Position: | VBU ± 15° | |
| Overall Length: | 160 mm | 65/16 Inches |
| Light Centre Length: | 89.0 ± 0.5mm | 31/2 Inches |
| Factory: | Leicester | United Kingdom |
| Date of Manufacture: | 1974 November | Date Code: 480 11 |
| Original Value: | GB £10.37 (1974) | |
