Osram NAV-E 70W/NB for City of Leipzig

Following the 1990 German reunification the former Eastern territories were opened to foreign competition, leading to the 1992 bankruptcy of the former state-run lampmaker and monopoly holder, Narva. Problems then became apparent with the new Western HPS lamps, which were failing quickly or not striking, in particular the 70W rating in Leipzig area.

The cause is believed to have been due to greater design tolerances with old East German ballasts and ignitors, plus harmonisation of European mains voltages from 220V±6% and 240V±6% to 230V±10%. The wider mains tolerance meant that in many regions there was no actual change, but in others where the electricity grid required upgrading, the average voltage did increase, and caused a power increase in lamps. Perhaps because Narva lamps had not been so highly optimised as foreign types, and may have had slightly cooler-burning arc tubes and/or lower xenon fill pressures, they were able to tolerate the elevated powers and strike on weaker ignitors. But for Osram and Philips it was a disaster.

In 1992 Osram solved the problem with the launch of this NAV-E 70W/NB lamp, where NB = Neue Bundesländer, or New Federal States. It was sold exclusively in former DDR territories and features a reduced arc voltage, such that when driven at increased currents the lamp power does not rise too high and it meets its life claim. If driven at standard IEC ballast conditions, it only achieves 53W. It also appears to strike more easily than the standard model. During 1993-94 Philips briefly offered an equivalent 'SON-G' for Germany. Osram maintained its production until as late as 2007, by which time the older control gear had been replaced and there was no longer a need for this highly unusual lamp.
Manufacturer: Osram GmbH
Lamp Power: 70 Watts
Lamp Current: 1.2 Amps
Lamp Voltage: 73 Volts
Cap Type: E27/27 Ni plated brass + Vitrite
Bulb Type: E-70 E-22 in eighths/inch
Bulb Finish: Calcium Pyrophosphate Soda-lime glass
Electrodes: Backwound Tungsten BCT emitter
Arc Length:
Atmosphere: Inner: Na,Hg | Xe Outer: Hard Vacuum
Luminous Flux: 5600 ℓm
Luminous Efficacy: 80 ℓm/W
Colour Temperature & CRI: CCT: 2000K CRI: Ra 20
Chromaticity Co-ordinates: CCx: 0.526 CCy: 0.418
Rated Lifetime: 18,000 h to 50% survival
Warm-up & Re-strike Time: 5 minutes 5 minutes max.
Burning Position: Universal
Overall Length: 156 mm 41/8 inches
Light Centre Length: 104 mm 23/4 inches
Factory: Berlin Werk-SB Germany
Date of Manufacture: 2003 Feb Date Code: q328
Original Value: Unknown
References: 1) Osram Lamp Catalogue, 2002/2003 Germany p5.19 & 5.32
2) Private communication, Michael Glück, October 2021
3) Osram NAV-E 70W/NB of Michael Glück at Lighting Gallery website
4) Philips SON-G 70W Lamp of Michael Glück at Lighting Gallery website
5) Philips SON-G 70W Lamp of Max Gendre at Lighting Gallery website