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Thin Phosphor Coating on Alto Lamps

Thin Phosphor Coating on Alto Lamps

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Here I have Philips Alto Lamps that my Dad and I installed at our basement several years ago.

Here you can see thin coating of the phosphor that you can actually see the cathode assembly.

P8050230.JPG P8050229.JPG basementlight.jpg P5240154.JPG

Light Information

Light Information

Manufacturer:Philips
Model Reference:F40T12/COOL WHITE PLUS
Lamp
Lamp Type:F40T12
Base:Medium Bi-Pin
Fixture
Location:Our Basement
Electrical
Wattage:40 Watt
Voltage:120VAC, 60Hz
Optical
Color Temperature:4100K
Physical/Production
Factory Location:USA (Bulbs)
Fabrication Date:May 2005 (E5 on Etch of the Bulbs)

File information

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Filename:basementlight.jpg
Album name:rjluna2 / Lighted Gallery
Keywords:Lanterns
File Size:25 KB
Date added:Jul 05, 2009
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don93s
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Jul 05, 2009 at 04:09 PM Author: don93s
I see certain newer Sylvania lamps like this too...such as the F40 Design 50's, only they don't use cathode shields.
Bamaslamma1003
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Dec 19, 2009 at 06:32 PM Author: Bamaslamma1003
I had a set of those once. They got broken. They had thin phosphor on the ends as well. I've also seen a few F96T12 slimline Altos with thin phosphor on the ends as well.

Power provided by Alabama Power, 120 volts 60 Hz. House is an LED free zone, tungsten and linear fluorescent only.

joseph_125
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Dec 19, 2009 at 06:36 PM Author: joseph_125
I've also seen a lot of Philips fluorescents that have thin phosphor near the ends. I also have a GE F20 Chroma 50 with a tiny spot on one end that has no phosphor. It's just big enough to look inside the lamp and see the cathode on that end.
Alights
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USA (120V 60HZ)


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Jan 16, 2010 at 07:18 PM Author: Alights
Why do Altos have this thin phosphor on one end? and it dosent seem to be an issue with the T12 lamps. maybe something with the manufacturing process.

Magnetic ballasts and old school electronic only zone!  No T8 instant start

rjluna2
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Robert


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Jan 16, 2010 at 07:25 PM Author: rjluna2
I think it has to do with phosphor crystal arrangement on the coating. I can see in a certain angle of the bulb that is completely opaque at the end of the bulb and other angle, I can actually see translucency of the same end.

Pretty, please no more Chinese failure.

RCM442
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Jul 02, 2010 at 07:53 PM Author: RCM442
Watching some of the videos of how these are made, it seems Philips pours the phosphor in from one end, leading it to get thinner and thinner as the lamp gets coated, that seems like it may be a reason the phosphor is thin at this end!

Linear fluorescent will never lose to LED!
I am not Anti-LED, as I have some in use at my house.
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icefoglights
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Jul 02, 2010 at 10:04 PM Author: icefoglights
It seems like many of the GE F40/UTSL lamps have thin phosphor at the ends too.

01010010 01101111 01100010 01100101 01110010 01110100

dor123
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Jan 11, 2011 at 09:19 AM Author: dor123
I have noted that the majority of the american fluorescent lamps have cathode guards, while none of the modern euroepan flureoscnet have cathode guards.
Why this is the case?

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

Mercury Man
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Jan 11, 2011 at 10:15 AM Author: Mercury Man
Cathode guards contain the emitter materials that are spurned off during the lamp's lifespan, thereby reducing end-blackening. As to why American lamps have this and European lamps don't, I have no idea.
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Jan 11, 2011 at 11:44 AM Author: TL8W
In regards to the topic of "thick and thin", most lamps have a "thick" end and a "thin end" which is certainly due to phosphor pouring methods. I have seen this on Atlas(Thorn) and Osram(GEC) lamps in the UK (back in the days) and certainly on Sylvania and Philips ALTO lamps in the US. The variation of thickness seems less obvious on European "Polish" Philips T8/T12 types but is is still there. Where I don't see it is on lamps that tend to use a "powdery" appearance phosphor - such as on UK Philips lamps from late 1970s. Finnish AIRAM lamps from same period also seem very "even ended".

But I can remember viewing failed lamps on switchstart circuits where the "thin" end depletes its emitter and during closed starter mode the electrode was always visible.

@dor123: Cathode guards on US lamps from what I have seen appear to be mainly on long T12s, at least in 2009 when I was last in the States. And Philips tended to include them in T8s too, even down to fifteen watts (according to the Kitchen & Bath - 830 specimen that came back to England with me). US GE seem to exclude guards on T8s, as does Osram-Sylvania. Over this side of the pond, Philips have done some odd things with cathode guards: French lamps made up to 2007 in 2ft & 4ft seemed to have a guard at one end only (I never found any explanation for this). Their Polish lamps seem uniformly guarded until the summer of 2010 when new lamps display a seemingly bare-cathode glow when illuminated - I've seen no failed lamps yet! In 2008 Sylvania seem to have removed guards from anything in T8 below the 58W (5ft) size. GE (Hungarian-made) continue to guard their entire T8 line whilst T12s of 4ft and below are unguarded. Osram (Germany) also did this odd thing of guarding only one end (randomly - as opposed to Philips who guard the tail end in all single guarded lamps). Whether one-end-only guarding continues with Osram I cannot say, but their russian T12s were certainly bare-cathode last time I looked! Crompton (Chinese) and Narva (E Germany) guard their entire range. Aura (Sweden) seem to have an unusual closed guard covering much of the cathode creating a very dark end-shadow when lamp illuminated.

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SeanB~1
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Jan 11, 2011 at 12:23 PM Author: SeanB~1
I think the guard at one end only is to hold the mercury dosing capsule until it is activated by induction heating during the last stage of manufacturing after evacuation. Probably there to allow an optimum ( low) dose of mercury as opposed to a dosing via a dropper during the process.
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Jan 11, 2011 at 12:44 PM Author: AngryHorse
It also cuts down 50Hz flicker and slows down end blackening.
All my T8s, Philips, and GE, all have cathode shields.
Rich

"Beauty fades, dumb is forever".......Judge Judy Cheesy

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Jan 11, 2011 at 07:12 PM Author: don93s
Based on what I have seen so far here in the US, cathode guards are mainly restricted to Philips and other brands made by Philips and a few specialty off-brands such as Duro-Test (w/ion guard). The GE H.O. lamps also have them. Other than that, GE, Sylvania, and other off brands lack them.
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Jan 11, 2011 at 07:18 PM Author: RCM442
I've seen some of the newest eco lamps from sylvania now have cathode guards....

Linear fluorescent will never lose to LED!
I am not Anti-LED, as I have some in use at my house.
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Apr 25, 2019 at 12:43 PM Author: vytautas_lamps
You know, I don't think that thin layer of phosphor is a bad thing, if it is very good quality and glows brightly. After all, The phosphor in the lamp glows only the very top layer of it, and if it is a thic layer of it, the deeper layer can actually soak some of the light, making the tube dimmer than it could be. This was the no. 1 cause of soviet t8 tubes were very dim and very inefficient. This alto tube seems bright by the surrounding blackness if the background, even tho you can clearly see the cathode. So it's not a problem witch causes some major disadvantages of using such lamp. Maybe the blue spectrum penetrates the phopshor and makes things look cold and washout, but I don't think that is a problem, cause the blue glow is very light and not bright at all.

New lighting technologies is a pity fest everywhere you look. From LEDs that last only for two months, to a never-ending global starvation of t8 fluorescent tubes.
We shall reinforce ourselves with good old full mercury t12s and HIDs made to surpass one's life, and give them all the middle finger ;

rjluna2
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Apr 25, 2019 at 02:42 PM Author: rjluna2

I think it has to do with phosphor crystal arrangement on the coating. I can see in a certain angle of the bulb that is completely opaque at the end of the bulb and other angle, I can actually see translucency of the same end.

Here's what I mentioned earlier at this subject here

Pretty, please no more Chinese failure.

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