SOX-PSG with Philips Solid-state Getter

The SOX-PSG lamp was launched by Philips in September 2003 as the result of a successful attempt to eliminate early failures right up to the point of half its usual service life. This offered a tremendous advantage to end users who could avoid the expense of spot-replacements due to premature failures, which were commonplace with previous SOX lamps.

SOX lamps have traditionally employed a barium getter to maintain high vacuum in the outer jacket, to minimise heat loss and maintain high efficacy. However the barium film, usually deposited in the neck area of the lamp, is electrically conductive. If it contacts the leadwires of the stem it can cause decomposition of the glass stem by electrolysis, which may lead to leaks or cracking. The indium oxide heat-reflection film is also an electrical conductor, and if this contacts an electrified getter film it can draw sodium out of the arc tube and lead to very severe blackening as the sodium vapour attacks the indium film. To minimise this effect a gap is left in the indium film just above the getter, but the heat loss here can raise lamp voltage and power.

The PSG lamp replaces the barium getter with a so-called Philips Solid-state Getter. This consists of a zirconium-cobalt pellet on a stalk beside one electrode. The temperature here is just about sufficient for the getter to maintain high vacuum during life - but only for small volume lamps, hence SOX-PSG was only feasible in the 35W and 55W ratings. Because the conductive barium film is eliminated, reliability increases and failures before 6,000 hours are eliminated. The platinum catalyst from SOX-E lamps is also used to break down hydrocarbons for higher efficacy. SOX-PSG lamps can be identified by their special blue colour cap.
Manufacturer: Philips Lighting Ltd.
Lamp Power: 38 Watts
Lamp Current: 0.60 Amps
Lamp Voltage: 70 Volts
Cap Type: BY22d Blue Alkyde 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: 4,800 lm (@ 100 hrs)
Luminous Efficacy: 137.1 lm/W (@ 100 hrs)
Colour Temperature & CRI: CCT: 1700K CRI: Ra -44
Chromaticity Co-ordinates: CCx: 0.574 CCy: 0.425
Rated Lifetime: 18,000 hrs (70% survival) 12,000 hrs (92% survival)
Warm-up & Re-strike Time: 11½ minutes Instantaneous
Burning Position: Vertical Cap Up ± 110°
Overall Length: 311 mm 12¼ inches
Light Centre Length: 183 mm 7¼ inches
Factory: Hamilton Scotland
Date of Manufacture: September 2003 Date Code J3
Original & Present Value: £8.24 (2003) £11.63 (2014)
References: 1) Philips product launch, Hamilton Factory, 17th September 2003.
2) Philips Presentation, SOX-PSG, 2003.