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Can you lighting burnt out 40 W tubes

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jitun2

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Can you light burnt out 40 W tubes

Actually i found this as a challenge in this site

Code:
http://www.thinkcycle.org/tc-notes/show-note?tc_note_id=27219

"Challenge: Make a DC tube circuit using diodes an condensers for lighting burnt out 40 W tube lights

We make a DC tube circuit, where using only diodes and condensers we get a pulse of 600 V DC and this is used for lighting 40 W tube lights that have a burnt out filament. We have put back in use many such tubes (over 200 till now). We give this as an exercise to students. However we find some burnt out tubes don't work and some do. We do not know how to select the tubes from the junk tubes.

Vigyan Ashram
Pabal, Dist Pune 412 403
Tel; 02138-52326 Date:19 Feb 01 Updated by Yael on 2002-02-10 Updated by Yael on 2002-02-10

Posted by Yael on February 10, 2002 05:27 PM "
 
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I don't see where the challenge is?. Using an invert to run tubes off low voltage DC is commonplace, and they almost always don't use the tube heaters - they just apply enough voltage for the tube to fire without it.

As suggested above, this would enable you to use tubes with O/C heaters, but (in my experience - and I've changed two tubes tonight!) this is a very rare failure mode.
 
I may be mistaken but the electronic ballast that I just installed in my kitchen light connects to only one pin - and it would seem that failure of the heater might not affect the operation of the bulb.

I presume the electronic ballast (or the home made ballast) is in contact with the internal gas via the pin and heater filament. If the heater filament failure mode is such that there is not sufficient surface then the bulb might not light. It may be that the circuit tie to both pins at each end of the tube to improve the chances of success.

It would seem that a test fixture could be constructed that more or less operates the light. You might measure current, light output or other parameters as a way of predicting the useful life left in the tube. I do wonder how much actual life (at an efficient operating point) might actually be in a bulb with failed heaters.
 
I was distracted and meant to suggest that electronic ballasts that have been developed, tested, etc etc might be more appropriate over the long haul.
 
Well in normal operation the filament gets conected dirtelcy to mains over the balast.This makes it glow red-orange hot.Becuse its so hot it starts fireing electrons in the gas wich ionises the gas until its inoised enugh for the mains to start a arc in it.When a tube burns out the balast burns like like a normal light bulb.

But there is a nother way to start a tube all you need to do is apply enugh voltage to make a arc over in the tube.

Most 12V fluro-lamp drivers start the tube up this way.

And those compact flurescent bulbs use a combination of bouth.They try a high voltage pulse over it and at the same time heat the filaments.So if the high voltage spikes fail to start it you need to wait some time for the filament to heat up and it fire the tube.Those new ones start up near instantly.
 
It can be done with a normal switch start ballast providing one of the heaters works and the other still has enough emissive coating left; just short circuit the open circuit heater.
 
My 40W (34W when they are called "power miser") and smaller fluorescent tubes have filaments that glow the entire time the light is on, even when it is warmed up and the filaments aren't needed anymore. Therefore they waste about 10W of power and are what stops a tube from starting when a filament burns out. Sometimes a tube won't start because the contact needs wiggling to make better contact for the very high filament current.
I have never seen a "starter" on a fluorescent tube ballast but have seen them being sold.

This type with an inductive transformer ballast are being replaced soon with narrower tubes with an electronic ballast that will shut off the filaments when they are not needed. The new tubes are a different size to force people to replace the wasteful ballasts.
 
Most newer fixtures have that old kinds of starters that use bimetal.They keep oscilating until the tube fires up and there is not enugh curent left to keep it oscilating.

I hate those starters they need a long time to fire it up and they blink multiple timers before they do
 
I don't think it's anything to do with the current. They tend to oscillate until the fillaments are warm enough, in fact it often only starts when starter disconnects when the sinewave is at 90 or 270 degrees (peek voltage) so the tube starts due to the inductive kickback.
 
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