Sylvania Tru-Beam MR16 Peened Reflector - ELH

In 1965 the concept of the MR16 dichroic lamp was invented by Emmet Wiley of General Electric, and at once became very popular in all kinds of proejction applications. The original lamps had specular reflectors, and it was sometimes found that undesirable images of the filament and its supports would be projected in the beam, leading to a non-uniformity of the illuminated area. This was particularly troublesome for lamps having large filaments.

A solution was patented in 1965 by Levin & Lemons of Sylvania, with their invention of the 'Peened Reflector' featured here. It has small spherical depressions similar in appearance to a shot-peened metal surface, and these produce just enough controlled diffusion to achieve an almost completely uniform beam. The ELH lamp featured on this page was one of the first to make use of the peened reflector. It was developed for a new geration of 35mm slide projectors, whose optical performance was increased thanks to the MR16 lamp concept, and whose size and weight was greatly reduced thanks to the mains voltage filament which eliminated the need for a bulky low voltage transformer. The ELH was also used in photographic enlargers. Incidentally, these high voltage MR16 lamps have GY5.3 bases with flattened pins, to prevent the accidental insertion of low voltage GX5.3 lamps with round pins, for safety reasons.

After 1975 the peened reflectors were gradually replaced by superior multifacetted reflectors - another invention of GE's Emmett Wiley. Those featured improved optical efficiency due to reduced light scattering losses, and the glassworking tools were also considerably easier to produce and achieved longer moulding lifetimes than the peened surface designs.
Manufacturer: GTE Sylvania
Lamp Power: 300 Watts
Lamp Voltage: 120 Volts
Lamp Current: 2.5 Amperes
Cap Type: GY5.3 Molybdenum Pins
Bulb Type: MR-51 MR-16 in eighths/inch
Bulb Finish: Dichroic Mirror Quartz capsule
Filament Type: CC-8 Axial Coiled-Coil
Atmosphere: Bromine-Argon
Luminous Flux: N/A
Luminous Efficacy: N/A
Working Distance: 142 mm 5.6 inches
Working Aperture: 23.01 x 34.11 mm 0.906 x 1.343 inches
Colour Temperature & CRI: CCT: 3350K CRI: Ra 99
Chromaticity Co-ordinates: CCx: 0.406 CCy: 0.394
Rated Lifetime: 35 hours to 50% survival
Burning Position: Universal
Max. Overall Length: 44 mm 1 3/4"
Working Distance: 38 mm 1 1/2"
Factory: Drummondville Canada
Date of Manufacture: 1972 October Date Code: 22
Original Value: US $12.08 1974
References: 1) Sylvania Photolamps Catalogue, USA, 1979, p.29
2) Sylvania Audi-Visual & Studio Lamps Price Schedule AV74-1, USA, 1974, p.12
3) Sylvania Lighting Technical Manual, 3rd Edition 1978, Section 8 p.7
4) US Patent 3,428,800 - Spotlight Lamp, R.E. Levin & T.M. Lemons, GTE Sylvania, Filed 1965-Dec.
5) US Patent 3,891,421 - Method of making a controlled-diffusion stippled reflector by sag-moulding, R.E. Levin, GTE Sylvania, Filed 1973-Aug.
6) US Patent 4,021,659 - Projector Lamp Reflector, E.H. Wiley, General Electric, Filed 1975-Oct.