I never knew Philips now owned Osram. Osram SON lamps give off a poorer-quality, more orangey light than Philips ones as well. I suppose there will be a difference in lamp life there too.

Philips own the Osram SOX production line. I don't believe they own the Osram SON lamp line. As you mention Osram SON lamps are more peachy/pink in light where as Philips Master PIA SON is a more golden/white/yellow light.

The difference is very noticeable on a road where both lamp types are used.

Some interesting facts were given by Philips at today's ILP meeting with regard to SOX lamps.

* Replacing magnetic gear on 35/55W lamps with electronic, can give power savings that will payback the cost of the new ballast in 3 years. No electronic gear exists for larger lamps.

* China is a growing market for SOX lamps due to expanding road lighting, yet a shortage of power. SOX is still the most efficient light source.

* Philips SOX lamps have dimples along the arc tube to retain the sodium metal - otherwise it tends to migrate and condense on the colder u bend when the lamp cools. This uneven distribution of sodium increases run up time. For a dimpled arc tube (35W lamp) a run up time of 10 minutes can be achieved, for non dimpled it is typically 18 mins.

* The PSG SOX lamp (blue cap) achieves only a 7% failure rate after 12000 hours ( 3 years use) with practically no failures before 6000 hrs. For a standard lamp with non dimpled arc tube 50% of lamps would have failed at that point and 30% of standard dimpled lamps would have failed at 12000 hours.

* Efficiencies for SOX E lamps were quoted with 163 Lm/W for 36W SOX -E which replaces 55W standard SOX. This was one value I was missing from my data in the reference section.

Sotonsteve has mentioned seeing MA60s running 135W and 90W lamps. Whilst running 135W lamps is not an issue as the Philips 4135 leak ballast is suitable for both, I was a bit surprised it would run 90W as well.

From the Philips website, lamp voltages are:

90W = 112V, 135W = 164V and 180W = 240V. (currents all 0.8A)

Lamptech quote a lamp current of 0.9A so slightly different values of 125, 185 and 265V for 90, 135 and 180W respectively.

So I set up an experiment using a used Philips SOX+ 90W lamp running on a Philips 4135 ballast as used in a MA60.

Lamp voltage was around 155V cold, rising to 170V when at full power. Unfortunately I don't have an AC ammeter. So that gives 136W at full power - 124W at start. So in effect, the ballast sees the 90W lamp as a 135W one. Fortunately SOX lamps are tolerant to over voltage but I doubt the lamp lifetime will be that long, being run at 150% of its rating.

You would think the contractor's inventory would prevent a 90w lamp from being fitted in an 180w lantern anyway, unless they just never consulted it.

I have been carrying out a bit more experimentation with 90W SOX lamps in a bid to resurrect an old 140W SO ballast.

From my earlier post, Philips quote a lamp voltage of 112V @ 0.8A for 90W SOX which gives a lamp power of 89.6W.

Lamptech quote 125V @ 0.9A which gives a lamp power of 112.5W. I believe these figures date from the re-rating of SOX in 1968.

Lamptech quote 160V @ 0.9A for 140W SOI/H which gives 144W lamp power. These are Philips values from 1965.

For the earlier SO lamp they quote 155V @ 0.9A for 140W SO, which gives 139.5W. Philips figures 1943.

My ballast is a GEC item which dates from the late 1940s early 1950s. Lamp voltage is 150V @ 0.9A running a Philips 90W SOX lamp. That gives an actual lamp rating of 135W. Now given it is from the era of 140W SO, that would make sense, but it does mean when fitted with a modern lamp, it overruns the lamp by 50%. Circuit wattage is around 200W. Some ballasts of this vintage are still in service which goes to show that they really shouldn't be!

As a comparison I did a similar experiment on a 1960s Philips 4140 ballast for 140W SOI/H. Using the same lamp I got 160V @ 0.7A or 112W lamp power – very similar to the rerated SOX values from 1968. Circuit power was around 150W. Again a 90W SOX lamp is over run although not as much as on the GEC ballast. Again these ballasts are still in service.

My final comparison was with a Philips 4045 ballast for 45/60/85W SOI/H from the 1960s. This will run 35/55W SOX. Are these as bad when run with modern lamps?

Taking the Philips 1965 figures, 45W SOI/H is 80V @ 0.6A which is 48W lamp power, 60W SOI/H is 105V @ 0.6A which is 63W lamp power, 85W SOI/H is 160V @ 0.6A which is 96W lamp power. So what happens when this runs a 35W SOX lamp?

Well, 70.4V @ 0.5A, which gives a lamp power of 35.2W, and a circuit power of 75W. The best ignitor gear is around 65W circuit power,  so much better, and near enough bang on the correct lamp rating.

So the lesson is, whilst your 1960s leak gear can be relatively efficient for 35W SOX, its not for 90W SOX and should actually run 135W SOX - assuming the reactance is sufficient to achieve the starting voltage for the larger lamp.

And yes, my vintage ballast did work ok, although it needs a bit of a restoration due to damaged terminals....

With thanks to Versalift09 for the info, the Chinese are making SOX lamps with a new design of arc tube.

They also show them with GES caps.

At first thought those arc tubes would be a right pig to make without breakages, however CFL lamps are made in a similar shape so perhaps they have perfected it. With more arc tube per inch than for a conventional lamp there are more lumens. The efficiency of a low pressure lamp is driven predominately by heat loss, so more arc tube in the same envelope size raises efficiency.

They must have got good getters and glass seals to get lifetimes like that as well. Apparently China and Brazil are growing users of SOX lamps, given the size of China and that most areas outside cities will have no road lighting, you want the most efficient lighting otherwise the power required soon gets enormous. The growth in cities and rural electrification is growing far faster than power stations can be built, hence the requirement for efficiency.

I guess GES as they don’t have a history of B22d caps...

And just be sheer coincidence, last night thorncollector posted images of some 55W Chinese SOX lamps and also some 36W ones. Shame they aren't the curly type!

Wow that is fascinating stuff! It's interesting that all these years later they still haven't found a solution to the yellow colour that is often the downfall of SOX when it comes to lighting schemes aimed at tackling crime. Then again, I'm not complaining - if SOX was any other colour, it just wouldn't be the same!

Not sure I prefer the curly design... but still interesting all the same!

I wonder who will be the first person in the Ukastle/Yahoo discussion circles to get one of them? They do look rather unusual, and for some reason they remind me of "twister" iced lollies!

Looking at the picture though I'm not sure if the outer package is as long as a UK 90w, they look more like 55w in length.

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