48" florescent tube problem

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On Mon, 16 Nov 2009 16:13:17 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

Odd that you mention grounding as a possibility. There is a screw on the frame that is supposed to go to a ground wire, but there is no ground wire in the electrical box so I figured that the screws that now hold the fixture to the box would be sufficient ground. Maybe not?
They're new bulbs - and a much narrower diameter than the old ones.
One more odd thing, though not so odd in my house. The wall switch that operates the light works backwards. On is down. And I can't recall whether that worked that way before. It very well might have and there are two other switches in the house that work that way. I never bothered fixing them. I use this light so infrequently that I just don't recall.
I wondered if that indicates that the wiring in the fixture is backwards, but that doesn't make any sense to me. I mean, the switch is just open/close right? Even if the wires were reversed it doesn't seem that it would make the switch work the inverse way.
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It sounds to me as if you bought T8 bulbs to go in an old fixture made for T 12 bulbs. The bulbs will fit, the ballast cannot drive T8's. If you installed new fixtures, this is not the problem assuming you have T8 ballasts for T8 bulbs.
If they are the old fixtures, the ballast(s) can be shot or the tombstones (the things that hold the bulbs) can be shot or have a loose wire connection.
The newest bulbs are T5's, same problems.
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While you're discussing the difference- What *is* the difference between the T8 & T12 bulbs?
I just bought a dozen ballasts of ebay for the T8s and fixed the pile of dead $10 shoplights in the corner of the garage. [worked out to about $6 a ballast] I bought a case of T8s for them.
I just ran across a 1/2 box of T12s- will they work ok in the new T8 lights?
Thanks Jim
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Nope, nope, nope. The ballasts have to be compatible with the bulbs. If you got T8 ballasts for that kind of money, they must have been hot or the person had absolutely no idea of their cost.
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T8 requires less current and more voltage than T12.
If you run T8 bulbs from T12 ballasts, they may or may not start, and they may flicker or have unstable operation if they do start. If they run, their life is likely to be shortened.
T12 bulbs powered by T8 ballasts will be underpowered. This *may* shorten their life. 34 watt T12 bulbs may flicker or swirl or bead with T8 ballasts as well as run dim.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Thu, 19 Nov 2009 00:59:58 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

Ok, just hold on a minute here. The new tubes I bought for the new fixture were much smaller (diameter) than the old tubes in the old fixture. Do I need to check that they are either T8 or T12 and also what the fixture is?
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dgk wrote: ...

The smaller (1") diameter are T8; T12 are 1-1/2" D.
<http://www.ehow.com/about_5426758_fluorescent-vs-bulbs.html
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Ok, then I have T8 and the fixture is for T8.
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Don Klipstein wrote:

That reminded me of an old florescent bulb and starter tester an old employer had. It was probably out of an old hardware store. Set the switches for the wattage bulb, put one end of the bulb in the unit, a cord and plug went to the other (top) end. Hold a switch closed for a second then release. (mimicking a starter) If it lights it's good, if not, it's bad. If it's good then turn a switch to "starter", install the starter and hit a switch to see if the bulb lights.
Anyway what reminded me of it was a suggestion to install the starter reversed polarity and test it again to see if it works that way. I had seen the same suggestion in an old (early 50's) jukebox manual. I think I may have had a few work that way, but they were dead again by the next day, so I always replaced the bulb and starter. The cost of the bulb, even if not needed, saved a lot more money than the cost of a call back service call.
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