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White SON This is a 50W SDW-T high-pressure sodium lamp from the Philips Master series. I do find the small HPS lamps run with a very yellow output, so was interested to see what this can do. It is running on a magnetic ballast here, which isn’t ideal but it is still whiter than a 50w SON/T. I don’t have the correct ballast but tempted to run it on a 60W electronic ballast now knowing how much you can push HPS lamps for a short time. The larger absorption gap is much more noticeable than in SON lamps as can be seen in the spectrum. Keywords: Lamps

White SON

This is a 50W SDW-T high-pressure sodium lamp from the Philips Master series. I do find the small HPS lamps run with a very yellow output, so was interested to see what this can do. It is running on a magnetic ballast here, which isn’t ideal but it is still whiter than a 50w SON/T. I don’t have the correct ballast but tempted to run it on a 60W electronic ballast now knowing how much you can push HPS lamps for a short time. The larger absorption gap is much more noticeable than in SON lamps as can be seen in the spectrum.

_IMG0248.JPG _IMG0245.JPG SWD-T.jpg 1000037625.jpg _IMG0235.JPG
Lamp/Fixture Information
Manufacturer:Philips
Model Reference:SDW-T
Lamp
Lamp Type:HP sodium
Electrical
Wattage:50w
File information
Filename:SWD-T.jpg
Album name:Tuopeek / High Pressure Sodium
Keywords:Lamps
Filesize:392 KiB
Date added:17 Jun 2026
Dimensions:2400 x 2372 pixels
Displayed:12 times
DateTime Original:2026:06:17 16:16:56
Exposure Time:1/125 sec
FNumber:f/5.6
File Source:Digital Still Camera
Flash:No Flash
Focal length:55 mm
ISO:800
Model:NIKON D3400
Software:Adobe Photoshop Elements 2.0
White Balance:0
URL:https://trad-lighting.net/gallery/displayimage.php?pid=1334
Favourites:Add to Favourites

Comment 1 to 2 of 2
Page: 1

Max   [Wed 17 Jun 2026 at 21:09]
Strange. Have you measured the lamp's rms voltage? It is indicative of the light color and should be around 92 V at the nominal color point (2500 K / 83 Ra8). If your lamp is not too worn out (as the picture suggests) and the ballast operates normally, then you should get a nice warm-white light color on the 50 W SON choke - what the lamp was designed for (plus the voltage regulator, which is useful only to maintain a stable light color point through life, so this part is not essential in your case).
Tuopeek   [Thu 18 Jun 2026 at 10:02]
I checked the lamp voltage after giving it some extra time to warm up at 102.6V on 245V mains. I think I didn’t give it enough time previously. The discharge seems a little unstable at the start and behaves as it may self-extinguish for a few seconds. So, although new, may be slightly faulty or needs a good run in. I was quite naughty and gave it a run up on a CPO 60W eballast which worked fine with perhaps a slightly whiter output, as you would expect but still with the unstable arc starting. Although, today it seemed a lot less eager to ignite but worked fine once started. I know I should stop torturing lamps for curiosity Laughing

Comment 1 to 2 of 2
Page: 1