How do flourescent bulbs die?

[Bill, KD0HG]

OK, our receptionist asked me this morning, and I kinda said, "duh!".

Why/how do fluorescent light bulbs fail- or wear out?

There's no filament inside, just a blob of ionized, glowing gas that should never 'wear out' or ever be used up.

I have wondered that myself in the past...Anyone know the failure mode?

[The Slab Bacon]

It's all those "black robed gangsters"

A conspiracy theory, I tell ya! ! ! ! 

[ka3zlr]

There's a couple of ways actually, gas bleed off, element failure on the ends, either end,.. and the bulb will show a dark color at the end....and then there's the ballast but that's easily figured out though.


73
Jack.

[flintstone mop]

It seems that the ballast keeps something going in the filaments at each end of the tube and the result is an ultraviolet light that energizes the coating???
Bits and pieces of info from
Phred

[W1RKW]

the company I work for spent 10s of thousands of dollars converting from conventional ballasts and flo tubes to switching or solid state ballasts and a different flo tube to work with the SS ballast. It seems we have facilities replacing these tubes more often now since they made the conversion. Maybe the tubes are crappy.  This going green thing in my company IMO is poised to backfire based on this observation and cost more money overall.

[n4wc]

How do flourescent  bulbs die?

I have it on good authority that they do not emit light, but absorb darkness.
When the tube is full of darkness; you can tell by looking at the ends of the bulb; they don't work anymore.   

73 Bill

[WBear2GCR]

They have a filament on each end... the filament gets hot, it emits electrons that are accelerated by the HV from the ballast causing the gas (with mercury) inside to become a plasma and emits UV that in turn hits the rare earth fos4s (phosphors) that emit RGB in the proper balance to meet some deg kelvin color standard... you'd think that if rare earth was so damn rare that they'd really want to recycle all those CRTs and flourescent light bulbs??

Anyhow, the filament gets used up and then the thing won't ignite and create the plasma... you could put HV on the ends and make it light, or else use RF or a Tesla coil and not need any connections at at all!!

           

Now you know the rest of the story...

             _-_-WBear2GCR

[W7TFO]

Not all fluorescents have filaments, the rapid-start types have just one pin on each end.  They fire on higher voltage alone. 

They get black ends and fail as well.  Methinks the prolonged ionization of the gas inside just uses up all the available material.

On the two-pin jobs, lots of times you can flip it end for end and it will run some more, as they only use the filament to start it on one end.

[KE6DF]

I bought two screw-in compact fluorescents (actually they weren't that compact) back in 1990. Still going strong after nearly 20 years. Doesn't seem like the current ones last as long. The 1990 ones cost about $20 ea if I remember right.

[flintstone mop]

How do flourescent  bulbs die?

I have it on good authority that they do not emit light, but absorb darkness.
When the tube is full of darkness; you can tell by looking at the ends of the bulb; they don't work anymore.      
73 Bill

That pretty much sums it up for this thread. Is that your story? And Are you sticking with it?

Fred

[W2PFY]

In fluorescent lights, a current regulated by a ballast is passed through mercury vapor. The current excites the mercury vapor, which emits photons in ultraviolet light. Since ultraviolet light is not part of the visible spectrum, fluorescent lights are coated with a phosphor that absorbs the ultraviolet light, and that then fluoresces, or emits photons of visible light.

[WBear2GCR]

Terry, I already said that...

TFO, afaik they all have filaments... all the broken ones i've ever seen have filaments there.
Now if they all use them, another story, that I am unsure about. But they probably do.

                   _-_-bear

[W2PFY]

Terry, I already said that..

Yes, I know Bear but I didn't say anything. I copied and pasted it in a mindless action.

As a side note, these lamps cannot be used with a dimmer. Maybe a grid could be used to control these  newfangled lamps.

[K3ZS]

They do have "dimmable" screw in fluorescent bulbs.   I had one blowup, but it was the electronic ballast that failed, not the bulb.

[nq5t]

Why/how do fluorescent light bulbs fail- or wear out?

There's a long section on Failure Modes at Wikipedia.    http://en.wikipedia.org/wiki/Fluorescent_lamp#End_of_life

Grant/NQ5T

[Bill, KD0HG]

Thanks, Grant. Exactly what I was looking for.