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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.

Screenshot_2026-06-03_134449.png _IMG0246.JPG SWD-T.jpg _IMG0249.JPG _IMG0251.JPG
Lamp/Fixture Information
Manufacturer:Philips
Model Reference:SDW-T
Lamp
Lamp Type:HP sodium
Electrical
Wattage:50w
Physical/Production
Factory Location:Belgium
Fabrication Date:2004
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:17 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 4 of 4
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
Max   [Thu 18 Jun 2026 at 22:10]
102.6 V and the light color is very yellow? It looks like your lamp is one that was affected by the aluminum contamination of the early 2000s. That's an issue which plagued certain lamp batches and caused a very significant reduction in life.
Tuopeek   [Fri 19 Jun 2026 at 08:28]
Certainly fits with the time of manufacture.

Comment 1 to 4 of 4
Page: 1