GEC SuperSOX 55W

Very soon after the introduction of Osram-GEC's first indium-oxide coated SOX lamps in 1967, the design was upgraded and by 1969 had been superseded by the "SuperSOX" range. Until this time SOX lamps from all manufacturers followed the Philips design having dimpled discharge tubes, in an effort to maintain uniform sodium distribution over life.

Whereas the dimples are essential for good performance with Philips lamps, Osram-GEC discovered that it was able to eliminate them due to the different nature of its IR coating process. Philips lamps have a relatively uniform IR coating thickness along the length of the lamp, and since the electrode-end of the discharge tube runs hotter than the U-bend this leads to a thermal gradient. The dimples are effective in avoiding the distillation of sodium from the hot end to cold. Meanwhile the GEC coating process achieves a graded film, and by arranging the thicker coating around the bend the root cause of sodium migration is solved.

When this was discovered, the GEC's 2nd generation indium SOX lamps were re-launched under the "SuperSOX" brand. The company extolled the virtues of its more robust dimple-free construction, and ring-shaped sodium reservoirs were added to the periphery of the U-bend to keep the main body of the discharge tube free of light-blocking sodium mirrors. However, the less uniform sodium distribution did lead to longer run-up times. Around this time the top support clip was redesigned with a stronger construction in which the former mica support discs were replace with a small steatite tube passing through the U-bend. Thermal insulation of the bend area was also enhanced by the addition of a large heat-reflective disc of mica.
Manufacturer: The General Electric Company of England PLC
Lamp Power: 55 Watts
Lamp Current: 0.9 Amps
Lamp Voltage: 109 Volts 410V Ignition
Cap Type: BY22d Mycalex Insulator
Bulb Type: T-50 T-16 in eighths/inch
Bulb Finish: Indium-tin oxide film Soda-lime glass
Electrodes: CCC-4 Beehive Black W + BCT emitter
Arc Length:
Atmosphere: Na | 99% Ne, 1% Ar Outer: Hard Vacuum
Luminous Flux: 7,650 lm (@ 100 hrs) 7,500 lm (average to 4,000h)
Luminous Efficacy: 139.1 lm/W (@ 100 hrs)
Colour Temperature & CRI: CCT: 1700K CRI: Ra -44
Chromaticity Co-ordinates: CCx: 0.574 CCy: 0.425
Rated Lifetime: >6,000 hours 50% survival
Warm-up & Re-strike time: 15 minutes Instantaneous
Burning Position: Vertical Cap Up ± 110°
Overall Length: 415 ± 10 mm 163/8 inches
Light Centre Length: 235 mm 91/4 inches
Factory: Shaw, Oldham England
Date of Manufacture: April 1978 Date Code: KD
Original / Present Value: Unknown
References: 1) Osram-GEC Lamp Catalogue, UK, 1975, p.30
2) Osram-GEC Technical Data, Low Pressure Sodium Lamps L4/HT, October 1969
3) Osram-GEC Low Pressure Sodium Lamps Brochure, 1972
4) Osram-GEC Low Pressure Sodium Lamps Brochure, 1981