Osram MBF/V Magnesium Fluorogermanate

Osram-GEC played a very important role in the development of the mercury fluorescent lamp and made numerous contributions to the phosphor materials employed. In fact the halophosphate chemicals, still widely used in today's standard fluoresent lamps, were developed by a team at the GEC's Hirst Research Centre in Wembley, North London. This particular lamp may be classified as being from the second generation of mercury fluorescent products, as it employs the magnesium fluoro-germanate phosphor.

The first generation fluorescent lamps were MAF types, which have have hard glass arc tubes and the 365.5nm mercury line is the shortest wavelength available to activate a phosphor. Coatings of zinc and cadmium sulphides were the standard materials, and are easily recognisable because of the yellow colour of the coating. In fact the zinc sulphide coating absorbed so much blue light that it was standard practice to add a little cadmium to the arc tube to generate extra blue lines, as well as few weak red lines as well. The phosphor boosted radiation in the orange and red regions.

MBF lamps however make use of quartz arc tubes, which transmit much shorter wavelengths of UV radiation. Magnesium fluoro-germanate was introduced with these products, a phosphor producing a brilliant red radiation at 658nm. Being a yellowish coating though, the blue mercury lines are absorbed somewhat, leading to an overall greenish cast from these lamps. Manganese-activated magnesium fluoro-germanate was superseded by europium-activated yttrium vanadate in the late 1960's which is neutral in colour and allows transmission of all mercury lines, and for deluxe colour lamps yttrium borate appeared in the 1970's.
Manufacturer: The General Electric Company of England PLC.
Lamp Power: 125 Watts
Lamp Current: 1.15 Amps
Lamp Voltage: 125 Volts 220-250V Mains voltage
Cap Type: B22d-25x26 Brass + vitrite
Bulb Finish: Mg4(F)Ge06:Mn phosphor Soda-lime soft glass
Bulb Type: PS-88 PS-28 in eighths/inch
Overall Length: 178 ± 5.5mm 7¼ inches
Light Centre Length: 133 ± 5.0mm 5¼ inches
Arc Length:
Electrodes: Backwound tungsten Double carbonate emitter
Atmosphere: Inner: Hg | Ar (8 atm) Outer: Nitrogen
Luminous Flux: 4,600 lm average through life
Luminous Efficacy: 57.5 lm/W average through life
Colour Temperature & CRI: CCT: ~4700K CRI: ~Ra=40
Chromaticity Co-ordinates: CCx: ~0.36 CCy: ~0.42
Burning Position: Vertical cap up
Rated Lifetime: 6,000 hours Rated to 70% survival
Warm-up & Re-strike Time: 5 minutes 10 minutes
Factory: Shaw, Oldham England
Date of Manufacture: May 1961 Date Code: SE
Original & Present Value: £2 19s 0d (1959) £45.93 (2005)
References: 1) Osram-GEC Lamp Catalogue, UK, 1960-61, p.21