Whats Up With This Tube.

[Truck]

i bought this tube yesterday its a t5 and it has a blue patch in the corner is it faulty

heres a pic look ate the top right bit of the tube its blue

 

[Rooster]

Difficult to see, do you mean the dark patch about an inch from the ends ? If so, it where the heaters have "burned" the inner coating... common if you have an old type ballast.
Could be the sign of a faulty starter (If you can see the heater glowing...)

 

[fifefish]

sometimes light tubes have an inbuilt starter(capacitor) so there is no need for a box to be cluttering up a shelf..
so that could be just the blank space where theres a starter..

 

[Rooster]

sometimes light tubes have an inbuilt starter(capacitor) so there is no need for a box to be cluttering up a shelf..
so that could be just the blank space where theres a starter..

...this is news to me !

 

[Lateral Line]

Fluorescent lamps that screw or twist into a socket have the starter, (electronic, not a ballast switch), built into the base. It is not in the lamp itself.

The end electrodes inside the evacuated tube "boil" metal off which tends to deposit around the end of the tubes. It is this that causes the darkening. Rooster is right that it is more common with older type ballast switches as the surge currents they generate are normally a lot higher then they need to be to strike the lamp. It can happen with electronic starters as well, particularly the "budget" brands.

 

[Rooster]

lets not get confused between a LAMP and a TUBE .... a tube contains NO active parts, just glass powder (The bit that emits the light) and an electrode or two.
The control gear is external.

A lamp... has all the bits required to work, built into one easy to swallow chunk... a common variety of these are "energy saving lamps" AKA "compact flourescent"

The terminology is not exact... tubes are often called "lamps" it can get very confusing !

 

[Lateral Line]

As usual Rooster, we get to debate semantics whilst basically agreeing. I call lamps "lamps" deliberately. A lamp is a device which emits light, (Dictionary.com). In the business, fluorescent tubes, W filaments, LED's, wick's etc. etc. are different technologies, but they are lamps.

How many forum members does it take to change a lightbulb?

1 to change the lightbulb
1 to post that the light bulb has been changed.
14 to share similar experiences of changing light bulbs and how the light bulb could have been changed differently.
7 to caution about the dangers of changing light bulbs.
27 to point out spelling/grammar errors in posts about changing light bulbs.
53 to flame the spell checkers.
6 to argue over whether it's "lightbulb" or "light bulb"
... another 6 to condemn those 6 as anally retentive.
2 industry professionals to inform the group that the proper term is "lamp".
15 know-it-alls who claim they were in the industry, and that "light bulb" is perfectly correct.
156 to email the participant's ISPs complaining that they are in violation of their "acceptable use policy".
109 to post that this forum is not about light bulbs and to please take this discussion to a lightbulb forum.
203 to demand that cross posting to Waffle, off-topic forum, and lightbulb forum about changing light bulbs be stopped.
111 to defend the posting to this forum saying that we all use light bulbs and therefore the posts are relevant to this forum.
306 to debate which method of changing light bulbs is superior, where to buy the best light bulbs, what brand of light bulbs work best for this technique and what brands are faulty.
27 to post URLs where one can see examples of different light bulbs.
14 to post that the URLs were posted incorrectly and then post the corrected URLs.
27 to post about links they found from the URLs that are relevant to this group which makes light bulbs relevant to this group.
33 to link all posts to date, quote them in their entirety including all headers and signatures, and add "Me too".
12 to post to the group that they will no longer post because they cannot handle the light bulb controversy.
19 to quote the "Me too's" to say "Me three".
4 to suggest that posters request the light bulb FAQ.
44 to ask what is a "FAQ"?
4 to say "didn't we go through this already a short time ago?"
143 to say "do a search on 'light bulbs' before posting questions about light bulbs".
16 to say, "I sent you a private message about light bulbs".
1 new forum member to respond to the original post 6 months from now and to start it all over again.

The "control gear" for a fluorescent lamp consists of some external circuit to generate a high enough voltage across the largely evacuated tube to "strike" it, and then limit the current though it to prevent it burning out quickly. A candle, which is also a lamp, needs a match to start it, and gravity to prevent it burning too quickly.

The "tube" of a fluorescent lamp contains the end electrodes, the low pressure gas, the phosphor, (which is where the light comes from), and a source of ions, (usually Hg). It would not work without these, so any or all of them can be considered active depending on your definition. The phosphor particularly so I would say.

A fluorescent lamp is a fluorescent lamp whether the control gear is built into the fitting, or external.

We can argue this if you like, but what is the point, I doubt we will ever agree.

 

[Rooster]

so whats a photon ?

 

[squeakytoy]

so whats a photon ?

A torpedo part