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PostPosted: Wed Jul 16, 2014 7:28 pm 
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Retrofit lamps have been available. These lamps were lower wattage than their mercury equivalents and brighter. Just as an example, I think there was something like a 110W SON retrofit for a 125W mercury. The wattages of these SON lamps were all different to the standard SON lamp ratings.


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PostPosted: Sun Aug 10, 2014 2:16 pm 
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A newly installed MRL6 has been noted burning with a very noticeable blue hue and at a low light output. What would cause this?

The lantern appears new and to be fitted with a standard 150W lamp and standard switching cell. Noted at about 2am so would have been on for a good few hours.


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PostPosted: Sun Aug 10, 2014 2:33 pm 
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Almost certainly a duff lamp - either one with a defective arc tube seal so that the temperature and pressure can't be reached to start the sodium discharge, or one which hasn't been filled properly with sodium in the first place.

A rare occurrence but not unique - it usually happens more with end of life lamps.


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PostPosted: Sun Aug 10, 2014 10:30 pm 
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The "blue hue" is probably caused by the mercury vapour discharge. HPS lamps contain sodium and mercury, the mercury helping to balance the colour output and also helping vaporise the sodium. This is why HPS lamps glow a white(r) colour before warming to yellow. I have noticed as HPS lamps age and start to go pink, the "mercury phase" where they glow white lasts longer (up to a minute or more for some of the lamps outside my house which must nearly be duff now) or, in some cases as Phosco152 says they never leave the mercury discharge phase. I personally have seen this only once so far, and the lamp seemed to phase between the whiter mercury discharge and sodium yellow as and when it pleased, and I think it also had a tendency to cycle. It looks like the council may have fixed it, most likely as it was reported - when I was a boy we lived across the road from a cycling lamp and it drove my mum mental, so I imagine they get reported probably quicker than fully blown lamps. If your MRL6 isn't cycling and the council don't do regular daytime switch-on-and-check of the lanterns it'll probably be like that for a while, essentially a gutsy mercury lamp. It may also be possible that even the mercury isn't vaporising and what you're actually seeing is purely an arc through the Xenon fill gas, personally I think this is rather unlikely but if it is true it will probably knacker the igniter.

I spectro'd a HPS lamp recently and when you break it down you can really see how many emission lines there are.
Image

The orange is the sodium D line and the green is also sodium, this line is weak to non existent in low pressure but as you up the pressure this line becomes more prominent. Anything left of that, so all the blue and violet lines, are from mercury. You can do this with any CD that has had the top label coating removed.

As much as I've said in the past that I'm not too fond of HPS, I am beginning to change my mind. Ever since getting one of my own to play with I've found that a good quality lamp with not too many hours on it gives nice golden light with - surprisingly - very good colour rendering. It becomes apparent though when lamps age as they go pink, much like mercury lamps go green, and it seems that a lot on the street which are worn out don't do the technology much justice.

This video taught me a lot about the science behind HPS:
https://www.youtube.com/watch?v=hArNwYgRgL4


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PostPosted: Mon Aug 11, 2014 12:10 am 
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I find when you live in an area where HPS is no longer used and its all white light you then start to miss the yellow light.


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PostPosted: Mon Sep 15, 2014 8:34 pm 
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Thought I'd post this, to illustrate the colour difference between fresh SON lamps and old worn out ones.

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It's completely unedited and the colour contrast is really that great. The left lamp, a relatively recent replacement is the correct golden yellow colour, the one on the right, an Arc that may not have had its first relamp yet, is burning very pink but amazingly not cycling yet. Brightness has dropped a little as well, the pavement below it isn't as well lit as under the fresher lamps.


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PostPosted: Tue Sep 16, 2014 4:01 am 
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It isn't that one lamp is new and the other isn't, it is because they are from different manufacturers. 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.


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PostPosted: Tue Sep 16, 2014 8:14 am 
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Oh, I agree different brands can have different colour tones, yes. However it's also fairly well acknowledged that colour shift can also occur as the lamp ages, I thought? Certainly, in this case it is due to ageing. I have lived close to this lamp for a few years now and have watched it get notably more pink!


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PostPosted: Tue Sep 16, 2014 11:35 pm 
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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.

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PostPosted: Thu Sep 18, 2014 3:05 pm 
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I have a Sylvania 35W SON-E lamp with an E27 cap and made in Belgium.


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