# Forum Home Renovation Lighting  Fluoro tube not working properly, middle is dim

## wozzzzza

I have replced a stuffed flashing fluoro tube with a new one, a 5 foot 36w long one.
I also replaced the starter.
i turned it on and it lit up straight away but the centre is dimmer than the ends. its about a third of the tube in the centre dimmed, any reason for this?? is the new tube stuffed??

----------


## applied

That is normal in new tubes especially good brands it will come good in with 40hours use.
T5 tubes the really skinny ones get what can only be be described as waves or clouds in them when new it's kind of disturbing really.

----------


## wozzzzza

ok cool, will wait a while and see what happens.

----------


## Smurf

I'm not sure of the exact reasons for it, but this sort of thing has become progressively more noticeable with each generation of tube. 
The old 40W tubes (the 38mm thick ones) just started up and that was it. 
Then came the 36W energy savers that put out the same light but are dim and "shimmer" when started up. They take a couple of minutes to warm up properly especially as they age.  
Next came the tri-phosphor 36W type which have the same characteristics as the older 36W but to a greater extreme. They often give the "dim in the middle" situation you describe and will also "shimmer" very noticeably all day in a cold environment.

----------


## applied

I have been lead to believe it is to do with the never ending attempt to lower the mercury content as this is the biggest environmental problem with this type of light and also with the newer lights the replacement of the balast with electronic control removing the need for starters completely. 
In commercial fitouts jobs we I can't speak for others actually run in the lights non stop for at least 100hours before the building is occupied to remove this cloudiness.

----------


## RustyNail

Yesterday  while upgrading a pump shed we put in an Osram "Neptune" IP56 dual 28W T5 fluoro (on sale at Turks at the moment) and I was surprised when first turned on that it was purplish at the ends and dim in the middle, but it came good after about 5 minutes. Turned on again about 2 hours later and it was fine immediately. I'll have to keep an eye out to see if it happens again.  
We used dual T5 fittings in a large shed (about 24 units in total) a few years back and they've never shown the same issue - perfect from the start, although they take a minute or two to get to full brightness.

----------


## bmcosta

Don't ask me why but all the ones I build do it but only out of the box. As you guys have mentioned once they're burnt in no problemo. 
Whereas with neon tubes it's a different story you need to burn them in and then once they age significantlythe mercury "walks" and you have dark spots all over the place. Sometimes You can take the unit down and shake the mercury around for a temporary fix but it's often best to replace the section.

----------

