ToshibaJapanese Style Mercury Lamp

The mercury lamp shown here is representative of the traditional product range developed by the Japanese manufacturers, when production began to commence there during the 1940's. The product range offered was characterised with its own unique ratings of 40, 100, 200, 300, 400 and 1000W.

Owing to the low mains voltage of 100V in Japan, the mercury lamps there are operated in the same way as American products, i.e. with a transformer type ballast to ensure a sufficiently high open circuit voltage. The lamp design is similar in many respects to the American lamps.

This Toshiba lamp still makes use of a relatively old-fashioned electrode construction style, and consequently the lumen depreciation through life is more rapid than for competitive brands. A few turns of fine single coiled tungsten filament wire are again coiled around the central shank of thoriated tungsten and welded in place. The assembly is then immersed in the emitter suspension, which fills the hollow void present inside the outer coil. Owing to the significant amount of emitter present on the outer surface of the electrode it is sputtered off relatively quickly leading to rapid blackening of the arc tube. The emitter is believed to be composed of the standard double carbonate mixture plus thoria and tungsten powder.

Mercury lamps of the more unusual 200W and 300W ratings such as this continue to find a niche market in the marine industry and may be found in service worldwide, owing to the great number of ships which have been constructed in Japan and then exported.
Manufacturer: Toshiba Electric Corporation
Lamp Power: 200 Watts
Lamp Current: 2.1 Amps
Lamp Voltage: 130 Volts
Cap: E39s/45 Nickel plated brass
Bulb Finish: Coated Yttrium phosphatevanadate
Bulb Type: BT-90 Borosilicate
Overall Length: 240 mm
Light Centre Length: 160 mm
Electrodes: Backwound coiled-coil Double carbonate emitter
Inner / Outer Atmosphere: Inner : Ar | Hg Outer: Pure Nitrogen
Luminous Flux: 9,900 lm @ 100 hours
Luminous Efficacy: 49.5 lm/W @ 100 hours
Colour Temperature & CRI: CCT: 3900K CRI: Ra 40
Chromaticity Co-ordinates: CCx: CCy:
Burning Position: Universal
Rated Life: 12,000 hours to 90% survival
Warm Up / Re-strike Time: 5 minutes
Factory: Yokohama Bay, Tokyo, Japan
Date of Manufacture: October 1993
Original / Present Value: JP¥ 4,420 (2003) £22.45 (2003)
References: 1) Toshiba Japan Catalogue 2003.