140 Watt SO/H lamp Warm-Up

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First developed by Philips Lighting in 1932, SO/H lamps were the first commercial sodium vapour lamps. These lamps feature a removable arc tube that is encased by an outer Dewar glass sleeve; reducing heat losses and allowing the arc tube to reach a sufficient temperature for the metallic sodium within it to vaporise.
Production of these lamps continued until the mid-1960s, when the SOI/H lamp was launched. This featured an integrated arc tube that could not be removed from the outer sleeve at the end of the lamp's life. The SOI/H lamp was, itself, later replaced with the fabulous SOX lamp, which remained in production until 2019.
The SO/H lamp seen in this video is made by Philips, and is rated at 140 W (the equivalent wattage for a modern SOX lamp is 90 W). It is fitted within a 1956 GEC Z9464 street lighting lantern, and runs on leak transformer gear of the same age.
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[@FrontSideBus]

Very nice to see these old SO lamps being ran up! An SO/I was the closest I came to one.

[@StreetLightOnline]

In an age-appropriate lantern too! What's odd is that I don't think that this particular lamp had ever been used until I acquired it. I did notice that it seems to blacken around the electrodes more rapidly than a SOX would. Ah, you're lucky there - my only SOI/Hs are 45 W. I can see why the integrated option overtook the SO/H design, even if they were probably more expensive as you were buying a new outer each time, as the inside of this lamp's Dewar jacket is quite dusty - something that seems to be common to the type.

[@FrontSideBus]

@@StreetLightOnline It was a 45w that I had. I no longer have it though, I traded it for a 250w MA/V.

[@StreetLightOnline]

A reasonable swap! I'd love to get hold of more early sodium lamps, though, just because they are so darned rare these days!

[@thelightingenthusiast]

Epic!

[@StreetLightOnline]

Absolutely - much better than the old version of this video, where the lamp was running on its own, and not in a period luminaire!

[@FinlaysFireSystemsElectrical]

What an absolutely beautiful lamp what size SOX lamp would these compare to as ive never seen one in reality (yet!)

[@StreetLightOnline]

90 Watt - I think that this was the largest version of the SO/H lamp produced; i.e. what became 135 / 180 Watt SOX didn't exist until later.

[@FinlaysFireSystemsElectrical]

@@StreetLightOnline Interesting! Motorways cant have been very bright back in the day 😂

[@StreetLightOnline]

They didn't exist at the time, of course, but even these early lamps would have been a vast improvement on the 1932 Purley Way scheme (the first road in the UK to use sodium lamps) - that only lasted a few years before being updated again, though the initial trial was still considered a success.

[@FinlaysFireSystemsElectrical]

@@StreetLightOnline Wow!!