CP/22 Twin Filament Studio Halogen Flexi-Pin

To coincide with the start of colour transmission by the BBC in 1967, a new twin-filament studio lamp was developed by Osram-GEC to offer more stable colour temperature during dimming. This was necessary owing to the relatively poor spectral sensitivity of early TV camera tubes, which were balanced for 3200K. The first lamps were incandescent, but in 1969 were upgraded to a halogen filling following Thorn's development of a quartz version. The original rating was the 2½/2½kW CP/20, joined soon after by this 1¼/1¼kW CP/22 as TV camera sensitivity improved and less light was required. That was found to be not quite sufficient for some studios, resulting in the 2½/1¼kW CP/57.

Rather famously one of the GEC lamps exploded during a live broadcast of the BBC News in 1982, showering the presenter, Jan Leeming, with fragments of hot glass. All hell broke loose the following morning in the corridors of power at GEC, and a swift solution was needed. It came in the form of the Flexi-Pin lamp featured on this page, developed by engineer Graham Skeldon. The reason for the explosion was traced to stresses which had been placed by the lampholder on the fragile glass-to-metal seals where the base pins pass through the glass. By introducing a small metal spring, it was possible to reduce glass stress and avoid a recurrence of the problem. At first the spring was made of brass, but later changed to molybdenum.

The rest of the lamp design is similar to earlier versions, although by this time the original G150 glass bulb had been replaced by this narrower T130. The mount construction has also been simplified somewhat, with all metal joints being made by close-fitting coils without need for welding.
Manufacturer: The General Electric Company of England
Lamp Power: 1250 + 1250 Watts
Lamp Voltage: 240 Volts
Lamp Current: 5.21 + 5.21 Amperes
Cap Type: GX38q Molybdenum Pins
Bulb Type: T-130 T-41 in eighths/inch
Bulb Finish: Clear Aluminosilicate hard glass
Filament Type: 2x C-13 Parallel Flat Grid
Atmosphere: Nitrogen + HBr
Luminous Flux: 27k / 27k / 56k lumens
Luminous Efficacy: 20.8 / 20.8 / 22.0 lm/W
Beam Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 3200K CRI: Ra 100
Chromaticity Co-ordinates: CCx: CCy:
Rated Lifetime: 100 hours
Burning Position: Vertical base down ± 45°
Overall Length: 235 mm 9 1/4 inches
Light Centre Length: 143 mm 5 5/8 inches
Factory: Wembley United Kingdom
Date of Manufacture: February 1986 Date Code: TB
Original / Present Value: Unknown
 
References: 1) Osram-GEC Lamp Catalogue, UK, 1985/86 p.232
2) An Improved Colour TV Lamp, Light & Lighting Journal (UK) December 1969 p.346
3) Private Communication, Graham Skeldon, Osram Wembley, 1994
4) Private Communication, Graham Watson, Victory Lighting, 1995
5) Private Communication, Roger Hume, GE Lighting Leicester, 1998