RLOD#10 (2020.05.14) 1984 Narva NC400-00

The Narva NC400-00 featured here is a late East-German medium-wattage metal halide lamp designed for general lighting purposes. It features a classic NTI fill chemistry and is designed to run on a 400 W mercury lamp ballast provided with a soft ignitor. Given its intended application, the lamp is provided with a clear elliptical jacket and can run at all positions, although its light color depends strongly on the operating angle. In the horizontal position the lamp emits a neutral white light while the light color becomes much cooler in the vertical position due to a reduced cold-spot temperature.

Narva first introduced this model in 1968 as the HQI 400W. Since then, the lamp saw several critical changes to its design, many of which occurred in the span of seven years, starting with a burner upgrade in 1977. The construction of this quartz vessel was changed to a single-piece design, with the sodium iodide dosage increased in order to produce a more neutral white light color (the original lamp had a daylight tone). Next, a nitrogen atmosphere was introduced in the outer jacket so as to limit the electrostatic charging of the burner, a process known for causing the electrolytic loss of sodium. Finally, a strip of Zr-Al getter was added to prevent the buildup of hydrogen. The last two changes occurred in 1984 and resulted in a better chemical stability of the lamp. This, combined with improved manufacturing processes and the use of better material grades, increased the lamp service life by 50 % to 6,000 h.