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Philips Ceramalux C150S63/Retrolux This was a eBay find. These HPS retrofit lamps similar to the Sylvania Unalux, but are designed to retrofit 175w M57/H39 lamps running on any ballast type. Unlike the Unalux lamps which use a Penning Mix and a starting antenna, these have a glow bottle ignitor. The spec sheet I have for these is from August 2004 and mentions this lamp using a BT-28 envelope, I wonder why Philips switched back to the BT-28 envelope for these. Keywords: Lamps

Philips Ceramalux C150S63/Retrolux

This was a eBay find. These HPS retrofit lamps similar to the Sylvania Unalux, but are designed to retrofit 175w M57/H39 lamps running on any ballast type. Unlike the Unalux lamps which use a Penning Mix and a starting antenna, these have a glow bottle ignitor.

The spec sheet I have for these is from August 2004 and mentions this lamp using a BT-28 envelope, I wonder why Philips switched back to the BT-28 envelope for these.

DSC05800.jpg DSC05810.jpg DSC01637.jpg DSC06383.jpg DSC06377.jpg
Lamp/Fixture Information
Manufacturer:Philips Lighting Company
Model Reference:C150S63/Retrolux
Lamp
Lamp Type:Retrofit High Pressure Sodium
Base:E39-Mogul
Shape/Finish:ED-28
Service Life:24000 hours
Fixture
Ballast Type:S63/H39/M57
Electrical
Wattage:150w
Optical
Lumen Output:15000 Lumens
Colour Temperature:2100K
Colour Rendering Index:25
Physical/Production
Factory Location:USA
Fabrication Date:September 2000
File information
Filename:DSC01637.jpg
Album name:347vPowerlite / Lamps
Keywords:Lamps
Filesize:986 KiB
Date added:30 Aug 2025
Dimensions:3072 x 2048 pixels
Displayed:572 times
DateTime Original:2025:08:30 10:59:54
Exposure Time:1/160 sec
FNumber:f/9
File Source:Digital Still Camera
Flash:Compulsory Flash, Return light detected
Focal length:68 mm
ISO:3200
Model:ILCE-6400
Software:Adobe Photoshop 21.1 (Windows)
White Balance:0
URL:https://trad-lighting.net/gallery/displayimage.php?pid=969
Favourites:Add to Favourites

Comment 1 to 8 of 8
Page: 1

Max   [Fri 05 Sep 2025 at 07:20]
Neat, that's a top-tier retrofit HPS lamp there! This Retrolux features an unsaturated-vapor arc tube with an integrated ignition antenna. The large purple ceramic plate near the base is a high-power resistor connected in series between the glow starter and the burner. It limits the short-circuit current when starter is closed, thus protecting the ballast from overheating risks. Interestingly, Philips used that resistor as a heat shield to protect the starter from thermal degradations.
347vPowerlite   [Sat 06 Sep 2025 at 16:38]
Thanks, I was wondering what the purpose of that large ceramic plate in the lamp, clever to use a large power resistor to protect the ballast from overheating. I also noticed there's a bi-metal switch that opens to switch the glow starter out of circuit as well. I've had this lamp fail to ignite on a HX ballast and that feature probably protected the ballast from the repeated starting attempts.

There's also a mica heat shield in the base, I suppose to protect it from the heat from the resistor.
Max   [Sun 07 Sep 2025 at 08:31]
Peculiar that your lamp failed to ignite. Unless its burner has leaked, those unsaturated vapor HPS lamps usually never cycle and end their life as a (blue) mercury-burning lamp.
347vPowerlite   [Wed 10 Sep 2025 at 17:34]
I don't think it was a problem with the lamp as I was able to get it running using two different 175w MV CWA ballasts. I later measured the HX ballast, and I suspect it underdrives lamps as I only measured 175w including ballast losses running a 175w lamp on that ballast fully warmed up.
Max   [Sat 13 Sep 2025 at 06:17]
Yes, there's something fishy with your HX ballast. Have you measured its output voltage without load? It should be 225 V at the very least.
347vPowerlite   [Wed 24 Sep 2025 at 22:18]
I just did, OCV on the ballast in question is 231V. Compared to my other 175w MV CWA ballast, which has a OCV of 244V. I didn't have problems with MV lamps striking on either ballast though.
Maxim   [Wed 08 Apr 2026 at 22:57]
Joe, these were listed as being BT-28 because EYE-Iwasaki manufactured these for Philips for some time out of Solon, Ohio. Not sure when production was moved in/out of Bath, NY however. I have an example made by Iwasaki, and two examples made by Philips. I really need to get around to running them up...!!!!!
347vPowerlite   [Mon 13 Apr 2026 at 04:04]
Interesting! I guess the explains why they were listed as BT-28

Comment 1 to 8 of 8
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