RLOD#16 (2020.05.22) 1984 Eye HF175PD

The “Power Deluxe” (PD) variant of Iwasaki’s high-pressure mercury fluorescent lamps is characterized by a high quality grade europium-activated yttrium vanadate phosphor with a well controlled grain size, applied with an optimum layer thickness. This, combined with an improved electrode processing method, resulted in 5 % increase in lumen output over equivalent lamps from the competition (8900 vs. 8500 lm initial level at 175 W), with a better flux maintenance through life.

Those lamps were aimed primarily at the Western market, for an operation both on standard series-choke ballasts and on high-reactance auto-transformers with a high current crest factor (1.8–2.0). As a result, the burner design is similar to that of European and American lamps (with an improved quality) and differs from that used in X-type lamps sold in Japan. This particular HF175PD was offered specifically in North America as this power rating was not common in Europe and Asia.

Typical of early BT-shaped mercury fluorescent lamps, the model shown here features a clear crown. That part of the bulb was left uncoated to prevent the release and deposition of phosphor material onto the burner when the frame was inserted during production. This issue, which could impact the lamp’s flux maintenance, was eventually solved with a better coating method and improved frame mounting springs. The present HF175PD is one of the last clear-top lamps produced by Iwasaki before they switched to fully coated bulbs in the mid-80s.