Osram Metal Halide Powerstar HQI 400W-71

Osram's first metal halide lamps were, like its competitors, based on tri-band chemistries. The first HQIL 400W lamp of the mid 1960s employed a large ovoid bulb coated with magnesium fluorogermanate phosphor. The company was quick to replace this with its own design based on the rare earth halide of dysprosium. Such lamps are characterised by a multi-line spectrum of exceptional colour rendering quality. A small amount of thallium iodide is added to bring the colour point onto the blackbody locus, and since the rare earth discharges tend to be highly constricted and as a result rather unstable, caesium is used as an arc-fattening agent. It was soon learned that these dysprosium lamps suffered short life, owing firstly to their sensitivity to hydrogen emissions from the glass bulb, and secondly due to the constricted arc being bowed to one side by magnetic forces induced by the current-carrying support frame.

Both of these problems were overcome with the 1971 introduction of the lamp on this page. The arc instability was overcome by making two versions, type -71 for vertical operation, and -70 for horizontal use which operates at about 10% lower efficacy. Arc stability was further improved by twisting the support frame such that the magnetic forces do not all come from one direction - but the arc is still somewhat bowed, as can be seen in the lighted photo.

The problem of hydrogen contamination has been solved by using a borosilicate glass having a lower concentration of hydroxyl ions. Rather unusually, this bulb has been drawn from tubing and domed at one end, instead of blowing into a tubular shape. Four barium getters serve to maintain high vacuum in the outer jacket, and there is no hydrogen getter.
Manufacturer: Osram GmbH
Lamp Power: 360 Watts
Lamp Current: 3.5 Amps
Lamp Voltage: 120 Volts
Cap Type: E40s/45 Ni plated brass + porcelain
Bulb Type: T-46 T-14½ in eighths/inch
Bulb Finish: Clear Borosilicate
Electrodes: Backwound Tungsten No emitter
Arc Length: 48 mm 1 7/8 inch
Atmosphere: DyI3,TlI,CsI | Ar:Kr85 Outer: Hard Vacuum
Luminous Flux: 28,000 lm @ 100 hours
Luminous Efficacy: 78 lm/W @ 100 hours
Colour Temperature & CRI: CCT: 5900K CRI: Ra 85
Chromaticity Co-ordinates: CCx: 0.330 CCy: 0.365
Rated Lifetime: 6,000 hours to 70% flux
Warm-up & Re-strike Time: 2 mins to 80% flux 10-15 minutes
Burning Position: Vertical ± 45°
Overall Length: 285 mm 111/4 inches
Light Centre Length: 175 mm 67/8 inches
Factory: Spandau, Berlin Germany
Date of Manufacture: January 1973 Date Code: kvX
Original / Present Value: DM 92,- (1972)
References: 1) Osram Brochure Q-M-Na Entladungslampen, 28 Januar 1972.
2) Osram Power Stars Technical Manual, August 1984.
3) Osram Lampenkatalog, Germany, Oktober 1965.
4) Metal Halide Lamps with Rare Earth Additives, A. Dobrusskin, Lighting Research & Technology V.3 No.2 (1971) pp.125-132.
5) Halogen-Metalldampflampen mit Seltenen Erden, A. Dobrusskin & H. Leyendecker, Technisch-wissenschaftliche Abhandlungen der Osram-Gesellschaft vol. 11 (1973) pp.163-188.