Dead Fluorescent doing something...

I am trying to figure out what causes this...

Category:

Education

Tags:

• swirling
• dead
• lamp
• fluorescent
• high
• output
• dying

[suzukir122]

I see... so this is a cold area. I've never heard of programmed starts being run in the cold. lol... and if you do catch one of those high outputs going out, be sure to record it because it is pretty interesting when their burning out.

[jecwhiz]

One did pretty recently....it flickered and flickered but worked....then fickered again...and worked for few hours...next day it was still working but there was an orange glow on the end......and eventually one tube loses vacuum and the other glows dimily as its series...

And it's not really a cold area....it was just an older type of use for frequent on and off before programmed start was more accepted or came out.....that's why.....those are run by motion sensors...

[suzukir122]

I see what you mean. I forgot about the programmed start ones... those ones are much easier on the cathode filaments and they don't blast the bulbs on like instant starts do... and the older ones that you guys used look like they may have been high output rapid starts... thought they were slimlines. Normally high outputs are used for colder areas or freezers.

[jecwhiz]

Those are actually high output T12 rapid starts with the recessed sockets which are basically bipins with plastic enclosed around them. They are out of service but the working ones still lights up. when it dies...it stays there dead....but we have some still in service at the freezer which glows dimmily and straining in the cold cuz of the cold! We have a few more in other rooms which aren't used as much but still fully in service! Those High output ones right here are from 1996...

[suzukir122]

It's not really the bulbs I hate... mainly the ballasts. They should have made rapid start ballasts for T8's. Then they would not only last longer, but they'd be brighter as well.

[jecwhiz]

Actually they make several types of ballasts for the T-8s....the ones shown here in the video lit and working actually has good ballast...those aren't instant start....those have the more expensive type of ballasts...called the Programmed start. They basically are same thing as preheat..but without the flashing and strobing on start up. They have like 2 second or 3 second delay with glowing ends, then turns on. They do last longer actually! The ones in the other room are instant and don't last!

[gent2000]

fix it

[andycflbulb]

@Nivicoman Oh, wow.

[Nivicoman]

@suzukir122 I've read that most of the deterioration of the filaments is during the starting process especially instant starts that use high voltage to strike the arc. The electron impact sputters off the thermionic coating more so than heating the filaments. I've not heard of programmed start ballasts till now but imagine they are a soft starter smoothly bringing up voltage till the tube strikes with less impact on the filaments.

[Nivicoman]

@AAVista Yeah the Mercury obviously and also the white phosphor coating isn't healthy.

[Nivicoman]

Any fluorescent tube with a broken filament will light pretty well off of a high voltage low current supply such as from a MOSFET driven flyback transformer. If there is a decent amount of thermionic emission coating on the filaments the tube will strike by high voltage alone then run in hot cathode mode as intended. The Instant Start type of tube works precisely that way in fact the filaments don't get current run through them it's just the coiled form is easier to heat up to emit electrons.

[Nivicoman]

@andycflbulb I believe so. The cathode material is so spent that the mercury can no longer boil and the tube is only ionizing the argon gas within. The mercury vapor makes 95% of the UV to excite the phosphor and the argon emits the other 5% of UV therefore the dim white glow of the phosphor.

[andycflbulb]

@Nivicoman question: is this what happens to 4' rapid starts when they die... the dim death glow white?

[TheSoxmania]

The lamp is unable to ionize, because of a lack of mercury, therefore it is doing what I call Traumatic ghosting.

[Nivicoman]

Have you seen them develop swirling arcs accompanied by orange glowing ends in their last hours or minutes of life? You can see a thin bright arc swirl around erratically when the cathode material is spent and current is being carried only on a small section of filament which heats orange and is spent even more quickly. When that's gone the lamp goes to it's dim whitish glow-dead, or if the filament breaks total darkness.

[AAVista]

@jecwhiz I wonder if you actually have seen a few of those bulbs literally go kah-blewy. Not only could you get pricked by shattered glass but the gasses that were still in the bulb can make you very sick. But when these bulbs burn out to the point that even the electrical contacts melt along with the possibility of broken glass, the stench may prove OVERWHELMING!!! Next to skunks, exploding fluorescent light bulbs can rank at the top of the stink chart!