Philips SOI Integral Sodium Vapour - 1st Generation

Following the invention of the Osram-GEC SOI/H Integral sodium lamp, Philips immediately started development of a similar design. Their work was usurped again in 1956 when GEC made a further improvement by adding heat-reflection glass sleeves around the discharge tube, the purpose being to reduce radiated heat losses such that the discharge tube diameter could be increased. The resulting decrease in discharge current density led to a still more efficient lamp. It took a number of years for Philips to catch up, and its early lamps were considerably inferior to the GEC solution.

This lamp is representative of Philips' first Integral design, which was launched in 1958 and was perhaps only in production for as little as two years. Its construction appears to be rather simple, based on the discharge tube of the Dimpled SO/H lamp permanently sealed into a narrow diameter evacuated outer envelope. The presence of the dimples possibly ensured a longer useful lamp life than the GEC equivalents by avoiding sodium migration through life. However there are no heat-reflecting glass sleeves, and as such the diameter of the discharge tube remains as narrow as in the dewar-jacket type lamps, and there can be no improvement in lamp efficacy.

An enamelled metal fork is present around one limb of the discharge tube, and is connected to the opposite electrode to facilitate lamp ignition. The discharge tube is mounted on a long glass stem to achieve the same light-centre-length as the SO/H lamps, and contains a barium getter film to maintain the outer jacket vacuum. In 1960 this lamp was superseded by the improved Philips SOI/H lamps with a heat-reflection glass sleeve.
Manufacturer: NV Philips Gloeilampenfabrieken
Lamp Power: 85 Watts
Lamp Current: 0.60 Amps 0.54A Starting current
Lamp Voltage: 140 Volts 200-250V Mains voltage
Cap Type: B22d/30x35 Ni plated brass + Vitrite
Bulb Finish: Clear Soft glass arc tube
Bulb Type: Inner: TU-12 x 28 Outer: T-38
Overall Length:
Light Centre Length:
Arc Length:
Electrodes: CCC-4 Black Tungsten BCT emitter
Atmosphere: Na | 99% Ne, 1% Ar Outer: Hard Vacuum
Luminous Flux:
Luminous Efficacy:
Colour Temperature & CRI: CCT: 1700K CRI: Ra-44
Chromaticity Co-ordinates: CCx: 0.574 CCy: 0.425
Burning Position: Vertical Base Up ± 95°
Rated Lifetime:
Warm-up & Re-strike Time: 7 minutes Instantaneous
Factory: Emmasingel, Eindhoven The Netherlands
Date of Manufacture: October 1958
Original & Present Value: Unknown