Mazda A-H1 Medium Pressure Mercury

This is representative of the first type of medium pressure mercury lamp to have been introduced to the USA, in 1934. Its design is a direct copy of the MA 400W lamp, which had been invented by Osram-GEC in England in 1932. Both its physical and electrical characteristics are virtually identical.

In America it quickly became known as the H1. Several different variants emerged over time,  This A-H1 is intended for burning in the vertical cap-up position. Type B-H1 has an inverted arc tube to permit cap-down use. It is important that the tip-off area is always uppermost, otherwise its slightly lower temperature may lead to the condensation of mercury inside the tip, thus preventing the lamp from fully running up. The D-H1 and E-H1 lamps were GE and Westinghouse's respective attempts at quartz lamps, whose more refractory arc tubes could be burned horizontally. The higher mercury vapour pressure also delivered increased luminous efficacy. A later F-H1 lamp was identical to the A-H1 but featured a more rugged mechanically fixed cap.

The discharge operates at a mercury pressure of 1.2 atmospheres, the same as the standard MA 400W.  The arc tube is fabricated from a blown aluminosilicate bulb. The main electrodes take the form of open tungsten coils impregnated with barium, strontium and calcium oxides as the emissive material. They are supported on a molybdenum T-piece, and the auxiliary ignition electrode is a simple rod alongside one of the main electrodes. As was standard practice with the American lamps, there is no platinum heat-reflective coating in the area behind the electrodes - hence the sensitivity to burning position, and the need to offer both cap up and cap down variants.
Manufacturer: General Electric Co. USA
Lamp Power: 400 Watts
Lamp Current: 3.2 Amps 5A starting current
Lamp Voltage: 137 Volts 220V starting voltage
Cap Type: E39s/41 Brass + vitrite
Bulb Finish: Clear Lead borosilicate glass
Bulb Type: T-51 T-16 in eighths/inch
Overall Length: 330 mm 13 inches
Light Centre Length: 197 mm 7¾ inches
Arc Length: 152 mm 6 inches
Electrodes: CCC-8 Triple Coil Ba-Sr-O emitter
Atmosphere: Inner: Hg | Ar (1.2 atm) Outer: Nitrogen
Luminous Flux: 16,000 lm (@ 100 hours)
Luminous Efficacy: 40.0 lm/W (@ 100 hours)
Colour Temperature & CRI: CCT: 5400K CRI: Ra 6
Chromaticity Co-ordinates: CCx: 0.337 CCy: 0.421
Burning Position: Vertical Base Up ± 10°
Rated Lifetime: 4000 hours (to 50% survival)
Warm-up & Re-strike Time: 7 minutes 7 minutes
Factory: Hoboken, NJ U.S.A.
Date of Manufacture: April 1945 Date Code: 64
Original & Present Value: US $10.50 (1947) £50.52 (2005)
References: 1) GE Lamp Catalogue, USA, 1948, p.27
2) General Electric Mercury Lamps Brochure H-1, 1935
3) General Electric Mercury & Sunlight Brochure, 1939
4) General Electric Mercury Lamps Brochure, 1947
5) Mazda Lamps Bulletin LD-1, C.E. Weitz, General Electric, 1939
6) Lamp photometric measurements