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PostPosted: Thu Sep 18, 2014 6:59 pm 
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GreatNorburyStDepot wrote:
Re: 35W SON-Es.  As a matter of interest, what is the manufacturer / brand of these lamps? Although I'm not up to date on the very latest types of discharge lamp, I do recall the standard 35W high pressure sodium is of US origin, hence the reason why such lamps are listed with an ANSI code ie 35W are S76, 50W are S68 and 70W are S62 etc. The code will specify the correct ballast to run the lamp within spec. According to an old GE catalogue I have of the mid 80s, a 35W HPS for universal burning with a E26 base has a nominal lamp voltage quoted of 52V, although more recent data from Philips suggest their Ceramalux SON would be 55V and pulling a nominal current of 0.76A. I would assume these figures are for lamps run on ANSI S76 ballasts on the American 120V supply. Would it be a different figure if operated on 240V, on cobbled together gear? The E26 base is another US quirk, for although being the same thread and pitch, the US cap is 1.5mm shorter than our E27. Both I suspect are interchangeable though.
35W SON-E? That's quite an interesting concept!  Those people who hated the fact that SON used more power than SOX, there's the solution!  Use lower wattage SON bulbs and accept the lower brightness level!


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PostPosted: Thu Sep 18, 2014 8:04 pm 
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Phosco152 wrote:
Osram SON lamps tend to be more pink/peach colour. Philips lamps are the more yellow/golden white colour.

Even old Philips lamps run the more yellow colour,  I have one which ran for 14 years, its now dim but not pink.

My childhood memory of SON lighting (circa. 30 to 35 years ago) was that the lamps were distinctively pink, and by comparison the current "gold" colour of SON is rather bland by comparison - it just looks like SOX heated up! If I could replace all my Philips SON lamps with Osram ones in one fell swoop, I probably would!

There is currently an excellent example of pink-burning SON lamps on the A12 Brentwood Bypass in Essex. The lanterns are WRTL Arcs mounted at 12m on stub brackets.

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This photograph from November 2013 was taken from the Weald Road overbridge in Brentwood.

Although I also believe it's different manufacturing processes that causes the different colour hues, this photograph does support the theory that pink-burning SON lamps aren't as bright and efficient as their golden-coloured counterparts. There is quite a drop-off in light underneath a pair of pink-burning SON lamps further along the carriageway. If this is a result of different manufacturing processes, it probably explains why pink-burning SON lamps are much harder to find these days - even on the Brentwood Bypass which used to have many more!

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Another view of the A12 Brentwood Bypass in Essex from November 2013, showing a patchwork quilt of pink and gold.

It would be excellent if SON went back to being pink again, but I can't see that happening!


Last edited by David on Mon Oct 09, 2017 10:42 pm, edited 1 time in total.

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PostPosted: Thu Sep 18, 2014 10:54 pm 
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Thanks for uploading those excellent photographs, David. I have never been along that stretch at night but would have automatically assumed that those Arcs (dating back to c. 2002) would be running to the inferior 'gold' type that you describe.

Incidentally, these were some of the first Arcs that I came across in this country.


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PostPosted: Fri Sep 19, 2014 1:39 pm 
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I never knew that about SON lamps but I have noticed that lamps in car parks tend to be more likely to be a pink colour or cycle on/off.


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PostPosted: Fri Sep 19, 2014 8:02 pm 
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sevenman, that's probably because they're abandoned and no one gives a flying, erm, frank about them. It's the same at a school near me, the bulkhead lights are mostly mercury, one is going green, and the only SON one that tries to light, cycles very rapidly. It's probably been like that for who knows how long and its only chance of getting noticed (as it's a school) is in the dead of winter, so that's another ~4 months away.

There's a Gamma 6 near me which appears to have stood the test of time against the onset of P567/As and Arcs, but its SON lamp burns very pink indeed. Could it be because it's older and worn out, or was it just a pink SON lamp to begin with? Who knows. Photo soon.

As for the colour of SON lamps, I'll clarify again that I'm not saying "pinking" is solely due to age, but aged lamps can shift in colour like the one I posted, and such colour shifts to tend to be "less yellow". There are some Beta 79s near me which are actually more yellow than SON tends to be and can be mistaken for SOX, as I almost did recently.

Perhaps the Brentwood Bypass had many more pink SON lamps because they were all relamped ;)


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PostPosted: Fri Sep 19, 2014 8:51 pm 
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Fantastic pictures as ever David!

The better brands of SON lamp tend to be more golden whilst the cheaper brands tend to be more pink. I recall many years ago seeing the differences with phosco152 in Portsmouth. The new Iridiums were fitted with Philips SON-T Pia Plus lamps, whereas many of the existing SON lanterns were fitted with Osram lamps.


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PostPosted: Fri Sep 19, 2014 9:06 pm 
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I believe the reason for the different colours are due to the efficacy of the arc. A higher temperature and pressure produces a more golden light (and a more efficient lamp).

Philips lamps are the highest quality and hence their more golden light.

Philips have invested much money in the research and manufacturing process to improve the sealing of the arc tube to achieve this. The difficulty of sealing the arc tube for high temperatures and pressures is why SON lamps (and MH for that matter) came along decades after the low pressure sodium lamp.

Cheaper lamps will obviously not be made to this standard and hence the more pink colour.

Like David I remember early SON lamps being more pink, in fact my recollections of early Hi-bay  fittings using SON lamps at school in the sports hall were actually of the colour being more orange/pink.

The better technology of the modern lamps would not have been available in decades past which would have explained the "non golden" colour when compared with today's lamps.

Another example of the colour of modern SON lamps, is Claire's competition winning photo of the M1 lighting in a snow storm.


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PostPosted: Fri Sep 19, 2014 9:16 pm 
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Interesting. I know that when Sodium is run under high pressure it produces a green line as well as the D line, but I wonder what it is that causes red to become more prominent, causing pink to emerge.

I wonder if it's due to pressure amount of how well sealed the tube is. Given some older tubes can go pink as well.

FYI I have a GE Lucalox lamp in my Arc not 10 feet away from me and it burns a lovely golden colour, the CRI is great as well. I guess they also make good quality lamps. I'm not sure if I'd like a pink SON lamp in my living room!

For what it's worth, I also remember SON lamps being largely pink when I was younger, but this is "only" early 1990s. But I do wonder if this is because SOX was more common so the contrast appeared to make SON more pink than it really was. Certainly on the motorways when we came up to Scotland, even to this day I remember seeing the "pink lights" (mostly hi masts) and then the yellow lights which I now know were SOX.


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