Philips Compact Fluorescent PL* 9W
The Philips PL* was the first family of compact fluorescent lamps designed for non-retrofit applications, and it set the global standard for virtually all later designs. It was originally conceived as an alternative to miniature T5 tubes in linear applications, but quickly established a powerful new market in downlighting. That led to numerous spinoffs of even more compact multi-tube variants with still higher power density.

The term 'PL' is derived from Philips' developmental name 'Pi-lamp', a reference to its novel π-shaped discharge tube. It was invented in 1979 by Jan Ridders, Rein van der Wolf and Cornelis van den Broek of Philips Roosendaal, who conceived a new method of joining parallel glass tubes via a small bridge. By spacing this a short distance from the tube ends, a cold spot is created where the mercury condenses. This allows lamp power to be increased while keeping the mercury vapour pressure low, which is important to maintain high efficacy. To withstand the high wall loading, PL* lamps make use of a thermally-stable green aluminate phosphor invented by Louis Vrenken for the SL* lamps. It is combined with red YOX phosphor plus some blue from the discharge to achieve a warm-white light of good colour rendering. Incidentally, the * in the lamp name denotes the use of that new phosphor, which delivers superior lumen maintenance.

The PL* 9W was launched in 1981, followed by 7W & 11W in 1982, and 5W in 1983. They are capped with a G23 base containing glowbottle starter and RF-supression capacitor. This simplifies luminaire wiring and ensures that a fresh starter is fitted with each new lamp. The 11W has too high a voltage for use on 120V mains, and a special 13W rating with GX23 cap was added in 1982 for those countries.
Manufacturer: NV Philips Gloeilampenfabrieken
Lamp Power: 8.7 Watts
Lamp Current: 0.170 Amps
Lamp Voltage: 60 Volts
Cap Type: G23 Al + Pocan-4235 PBT
Bulb Type: T-12.6 T-4 in eighths/inch
Bulb Finish: Y2O3:Eu3+, CeMgAl11O19:Tb3+ Soda-lime glass
Electrodes: Triple Coil Tungsten Triple carbonate emitter
Atmosphere: Krypton-Helium + Hg
Luminous Flux: 570 lm @ 100h 510 lm @ 2000h
Luminous Efficacy: 65.5 lm/W @ 100h 58.6 lm/W @ 2000h
Colour Temperature & CRI: CCT: 2700K CRI: Ra 81
Chromaticity Co-ordinates: CCx: 0.460 CCy: 0.414
Lifetime: 5000 hours Depreciation 4%/1000h
Warm-up & Re-strike Time: 2 minutes Instant
Burning Position: Universal
Overall Length: 163.5 mm 6.5 inches
Lighted Area: 106 x 27 x 13 mm 43/16 x 11/16 x 1/2 inches
Mass: 45 grams
Factory: Roosendaal The Netherlands
Date of Manufacture: 1982 March Date Code: C2
Original Value: GB £3.41 (1988)
References: 1) Philips Lamp Catalogue 1981 NL, pp.140
2) Philips Lamp Catalogue 1982 UK, pp.291-292
3) Philips Lamp Catalogue 1985 UK, pp.325-328
4) Philips Lamp Catalogue 1984 NL, pp.182-184
5) Philips Technical OEM Guide, PL-S Lamps, May 1994.
6) "PL" Lamp with an Integral Starting Device, W.Veenstra, 3rd International Symposium on Science & Technology of Light Sources, Toulouse, April 1983
7) 50 Jaar Philipslicht in Roosendaal 1948-1998, publ. Philips Roosendaal 1998, pp.38-39, 69
8) 60 Jaar Philips Roosendaal 1948-2008, publ. Philips Roosendaal 2008, p.67
9) Philips Roosendaal, Licht op een Veranderende Stad, publ. Stichting Ghulden Roos 2015, p.102
10) US Patent 4,324,447 - Method of Producing a LP Mercury Discharge Lamp - R. W. van der Wolf & C. J. van den Broek, Priority 1979
11) US Patent 4,335,330 - LP Mercury Discharge Lamp with Aluminate Phosphor - L.E.Vrenken, R.C.Peters, F.A.S.Ligthart, W.D.Couwenberg, Filed 1980