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GE Rectifying Fluorescent Type RF, F85T10 |
Although the lamp is operated on alternating current, it rectifies this internally such that direct current flows in only one direction. The discharge is conductive on both half-cycles due to the presence of two anodes. These take the form of a pair of graphite rods, separated by a Z-shaped iron plate and connected to a 2-pin cap. At the cathode end is a filament coated with emissive oxides, similar to that of a regular hot cathode fluorescent lamp. Although only two terminals are required, a 3-pin cap is used to ensure correct polarity. Two light colours were offered - Blue-White, using a pure magnesium tungstate phosphor, while this Industrial White example includes a small component of zinc beryllium silicate to reduce the colour temperature to a somewhat greenish 9000K. The resulting colour is ghastly, but it was intended to increase visual acuity for industrial applications.
The RF lamp has several advantages. It lights instantly, and there is much less stroboscopic effect due to its steady light output. In the early years its efficacy was higher than the hot cathode lamp due to reduced volt drop at the anodes. However, it requires much more complex control gear which made the total installation more expensive. In 1942 production of the ballasts and luminaires was prohibited due to wartime restrictions, and they never resumed production - although replacement lamps were made until the 1960s.
| Manufacturer: | General Electric U.S.A. | |
| Lamp Power: | 85 Watts | |
| Lamp Current: | Approx. 150 Volts | |
| Lamp Voltage: | Approx. 0.6 Amps | Approx. 2A Cathode Heating |
| Cap Type: | 2-pin @ anodes | 3-pin @ cathode |
| Bulb Type: | T-9 | T-29 in eighths/inch |
| Bulb Finish: | Industrial White | MgWO4 & (ZnBe)2SiO4:Mn |
| Electrodes: | Graphite anodes | Single Coil cathode |
| Discharge Length: | 1321 mm | 52 inches |
| Atmosphere: | Hg | Ar | 2-3 torr pressure |
| Luminous Flux: | 4,000 lm (@ 100h) | 3,000 lm (@ 3000h) |
| Luminous Efficacy: | 47.1 lm/W (@ 100h) | 35.3 lm/W (@ 3000h) |
| Colour Temperature & CRI: | CCT: Approx. 9000K | CRI: Approx. Ra65 |
| Chromaticity Co-ordinates: | CCx: 0.276 | CCy: 0.318 |
| Rated Lifetime: | 7500 hours | |
| Warm-up & Re-strike Time: | 2 minutes | Instant |
| Burning Position: | Horizontal with cathode >3" higher than anode | |
| Nominal Length: | 1461 mm | 57.5 inches |
| Factory: | Hoboken, NJ | U.S.A. |
| Date of Manufacture: | 1959 March? | Date Code: GEN L |
| Original Value: | US $4.25 | (1961) |
