Well, is it or was it quite cold, and has it brightened with time?
I got one out of a shed some years back when I needed light, and found it
exactly as you suggest, but after about half an hour it was normal.
Other than that, it could be either the ionisation at UV li is lower in the
middle somehow, or the phosphor is just thinner or not very good.
Brian

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From the Sofa of Brian Gaff Reply address is active
"Andrew Mawson" wrote in message
...
Never had this before. Fluorescent tubes in my experience either work at
full brightness, flicker, or just the heaters glow.

I had a flickering tube, installed a new one, and it started fine but was
noticeably dimmer in the middle than at the ends. When I got it out of the
store, one pin had been bent, which I bent straight and I tested the
heater at that end with a meter - it was ok. Now obviously it's had a
clunk to bend the pin. If it had spoilt the seal and made a 'soft' tube
I'd expect the heaters to glow brightly then burn out which it didn't. So
what process makes for a dim tube? End 25% at both ends is normal
brightness. Could the phosphor have been dislodged in the middle but not
the ends?

I'll leave it in place and observe it's progress as where it is is over a
shelf anyway.

Andrew