GE Lucalox LU250/BD/S with Superior Performance
GE's first Lucalox lamp was the 400W launched in 1965, and in 1966 it was joined by a 275W version. In 1967 both were redesigned with external amalgam reservoir to improve performance and reliability. The 275W arc tube was loaded a little higher than its 400W counterpart to achieve peak efficacy, but it was soon discovered that this was leading to problems of short life - the ceramic arc tube operated so hot that it began to sublime. In 1969 it had to be re-rated for lower power use, leading to the launch of the 250W lamp.

It would appear that the redesign from 275W to 250W may have been a rushed job because efficacy dropped greatly - to just 102 lm/W vs 125 lm/W of the 400W rating. Even the smaller 150W lamp achieved 107 lm/W. Around 1975 GE upgraded its 250W lamp, but instead of replacing the original it offered both side by side - this superior "S" lamp commanding a premium price to reflect its high output.

Arc tube dimensions have been reduced to achieve optimum wall loading. Additionally the outer bulb getter has been changed from the usual barium mirror to a stout L-shaped titanium rod, positioned such that it operates over the region 200-500°C. Under this condition it is an excellent getter for hydrogen - a gas not well sorbed by barium and whose high conductivity compromises thermal insulation of the arc tube. The new getter also absorbs less light than the barium mirror, but requires a longer vacuum pumping process, hence the high price. The result is a lamp achieving an impressive 120 lm/W. Remarkably GE produced both 250W lamps side by side until around 2000. The "S" version was then replaced by Lucalox HO, achieving still higher efficacy thanks to its elevated xenon pressure.
Manufacturer: General Electric Company U.S.A.
Lamp Power: 250 Watts
Lamp Current: 3.0 Amps
Lamp Voltage: 100 Volts
Cap Type: E39s/41 Brass + blue glass
Bulb Type: ED-57 ED-18 in eighths/inch
Bulb Finish: Clear Lead borosilicate glass
Electrodes: Double Tungsten Coils Ba2CaWO6 Emitter
Arc Length:
Atmosphere: Inner: Na,Hg | Xe Outer: Hard Vacuum
Luminous Flux: 30,000 lm (@ 100 hrs) 27,000 lm (average)
Luminous Efficacy: 120.0 lm/W (@ 100 hrs) 108 lm/W (average)
Colour Temperature & CRI: CCT: 1900K CRI: Ra 22
Chromaticity Co-ordinates: CCx: CCy:
Rated Lifetime: 24,000 hours to 50% survival
Warm-up & Re-strike Time: 3-4 minutes 0.5-1.5 minutes
Burning Position: Vertical Base Down ± 95°
Overall Length: 248 mm 93/4 inches
Light Centre Length: 146 mm 53/4 inches
Factory: Cuyahoga, NELA Park Cleveland OH, U.S.A.
Date of Manufacture: January 1977 Date Code: 61 -
Original Value: US $64.00 (1974)
 
References: 1) General Electric USA Large Lamp Catalogue, Form 9200, 1977
2) General Electric USA Large Lamp Catalogue, Form 9200, 1975
3) General Electric USA Large Lamp Catalogue, Form 9200, 1973
4) General Electric USA Brochure, High Intensity Discharge Lamps, TP107-R, USA, 1975, p.35
5) General Electric USA Brochure, Lampes à Décharge Haute Pression, 6374-482/ILD/F, France, 1980, pp.8&14
6) General Electric USA Large Lamp Price List, 1974.