Sylvania Capsylite High Efficacy with Diode Rectifier
In 1982 Sylvania introduced its Capsylite family of energy saving lamps, featuring a small hardlgass halogen tube encased within a traditional PAR38 lamp envelope. This delivered a modest energysaving along with doubled life. In 1985 a further gain was achieved by incorporating a small diode in the screw base, to reduce line voltage from 120V to about 85V by half-wave rectification with minimal power loss. For a given luminous flux, as filament voltage reduces its current must increase, and this necessitates a thicker tungsten wire. Thicker filaments take longer to evaporate to the point of failure, and part of this life increase can be offset by driving the filament harder. The resulting hotter operation leads to an increase in luminous efficacy.

A year later in 1986 the same technology was applied in this MB-19 shaped bulb, to create America's first energysaving halogen retrofit for an ordinary incandescent bulb. Offered in ratings of 42W, 52W and 72W to replace 60W, 75W and 100W incandescents, they delivered a significant energy saving while raising life to an impressive 3500 hours. The X-ray shadowgraph reveals the inner halogen capsule and small diode in the cool base area, along with the heavy-walled outer bulb which has to withstand a possible end-of-life explosion of the high pressure inner capsule.

This design concept works only on 60Hz mains as used in the Americas. At 50Hz the diode results in unacceptable levels of flicker. Moreover even in 60Hz countries the diode was found to interfere with operation on certain dimmer switches, which limited the popularity of these lamps so much that it was necessary to maintain the older diode-free designs in production despite their lower efficacy.
Manufacturer: Sylvania
Lamp Power: 72 Watts
Lamp Voltage: 120 Volts
Lamp Current: 0.6 Amperes
Cap Type: E26/25 Brass + vitrite
Bulb Type: MB-60 MB-19 in eighths/inch
Bulb Finish: Inside Frosted Borosilicate
Filament Type: CC-8 Axial Coiled Coil
Atmosphere: Bromine+Iodine in Kr Outer: Air
Luminous Flux: 1300 lm
Luminous Efficacy: 18.1 lm/W
Peak Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 2900K CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.444 CCy: 0.406
Rated Lifetime: 3500 hours to 50% survival
Burning Position: Universal
Max. Overall Length: 111.1 mm 4 3/8 inches
Light Centre Length: 85.7 mm 3 3/8 inches
Factory: Winchester, KY U.S.A.
Date of Manufacture: 1989
Original / Present Value:
References: 1) GTE Sylvania Large Lamp Catalog 1986 USA, pp. 12, 13, 16, 38, 39.
2) GTE Sylvania Brochure, Capsylite MB-19 Lamps, 1986 USA.
3) Progress Report 1986, Lighting Design & Application, November 1986 pp.27-28.
4) US Patent & Trademark Registration #73565612, GTE Sylvania 'Capsylite'
5) US Patent & Trademark Registration #73410910, GTE Sylvania 'Capsylite'