Svetotekhnika ДРИ175 (DRI175)
This 175W lamp is an example of early Russian innovations in metal halide lamps, which was produced on a limited scale during the 1980s. It appears to have been developed in an effort to improve the colour properties of metal halide lamps such that they could be applied more effictively in indoor lighting, in much the same way as simultaneous developments in Europe were taking place based around the more compact versions having R7s and G12 caps. It delivers an unusually low colour temperature warm white light having relatively good colour rendering properties, and was offered together with a smaller 125W rating.

The arc tube is pinched from a straight cylindrical piece of quartz without any special end forming, and no auxiliary ignition electrode. The area behind the electrodes is painted with a heat-reflective coating to raise halide vapor pressures. The material is green chromium oxide, typical of soviet metal halide lamps. Spectral analysis of the operating lamp would suggest that it is dosed with the halides of sodium, scandium and thallium, and employs a very high sodium mole ratio in order to achieve the low colour temperature. Ordinarily this would result in a rather pinkish colour light, but the addition of green thallium radiation brings the colour point close to the blackbody.

The arc tube is strapped to a split metal frame, the lower support being electrified and welded directly to the glass stem assembly, while the upper support is electrically floating. Current is carried to the far end via a flywire which has been positioned as far away as possible from the arc tube to minimise photoelectric sodium loss. There is a hydrogen getter of zirconium-aluminium in the outer.
Manufacturer: Svetotekhnika SPO
Lamp Power: 175 Watts
Lamp Current: 1.8 Amps
Lamp Voltage: 110 Volts
Cap Type: E40s/45 Nickel plated brass + porcelain
Bulb Type: T-46 T-14½ in eighths/inch
Bulb Finish: Clear Borosilicate glass
Electrodes: Backwound Tungsten
Arc Length: Approx. 30 mm 11/8 inches
Atmosphere: Hg, ScI3,NaI,TlI | Ar Nitrogen
Luminous Flux: 12,000 lm (@ 100 hrs) 10,050 lm (measured)
Luminous Efficacy: 68.6 lm/W (@ 100 hrs) 57.4 lm/W (measured)
Colour Temperature & CRI: CCT: 2850K CRI: Ra 65
Chromaticity Co-ordinates: CCx: 0.446 CCy: 0.401
Rated Lifetime: 4000 hours
Warm-up & Re-strike Time: 3 minutes ~10 minutes
Burning Position: Universal
Overall Length: 211 mm 83/8 inches
Light Centre Length: 130 mm 51/8 inches
Factory: Saransk Russia
Date of Manufacture: Q3 1987
Original / Present Value: Unknown
References: 1) Photoelectrical measurements of lamp, VBU @ 175W.
2) Virtual Museum of Electric Lighting (Russian).