Fluorescent light gave loud crack and then died. Quick advice appreciated.

My elderly, partially-sighted father has just phoned with the news that when he switched on a double-tube fluorescent light fitting this morning it emitted a sharp, loud noise ("more of a crack than a bang") apparently from one end, then flickered and died. He tried it again and it lit normally and stayed on.
What does this indicate? The tubes were replaced a month or so ago, after the old one had noticeably dimmed. The basic fitting is around ten years old and has never given trouble before.
I need to get this sorted out (and the light replaced, if necessary) fairly sharpish, so any advice would be welcome. Many thanks.
Bert
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On Mon, 19 Sep 2011 11:36:56 +0100

Sounds to me like a bad connection the first time. Maybe a good clean-up of the contacts might be in order, and check for signs of sparking.
--
Davey.

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Davey wrote:

Thanks for that: I'll see to it.
Bert
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On 19/09/2011 12:13, Davey wrote:

..or Power Factor correction capacitor failed. I've had this happen. Will run OK without it but it should be removed/replaced if that is what has happened.
Chris K
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Chris K wrote:

How could I tell if that's what's occurred? Will the component be visibly affected? What would be the consequence of leaving a damaged capacitor in situ?
Many thanks for the reply.
Bert
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On 19/09/2011 12:57, Chris K wrote:

Why replace, it doesn't consume any more power? Assuming of course the lighting isn't close to it's load limit.
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On 19/09/2011 13:17, Fredxx wrote:

No need to replace it, domestic fittings often don't have one anyway. Only relevant if you have a factory full on an industrial tariff.
The failure was obvious, end blown off the capacitor. The capacitor was 1960s vintage and sprayed the oil filling into the kitchen. Might well have been toxic PCB fluid but it hasn't killed me in 30 years:-)
Chris K
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I've just examined the light. The tubes were firmly and properly in place and there was no sign of blackening or sparking-damage at the contacts. The housings were clean and dry. With the cover off, the fitting itself also showed no sign of any damage or incursion.
The ballast unit is a lengthy (8" or so) module, completely sealed as far as I could see. Removing it would have meant taking down the entire fitting which I was loathe to do.
I tried the light few times and it worked perfectly: a quick, flicker-free start up, completely silent.
My father tells me, though, that over the past day or so, although the light has been working well in general, it has cut out and rapidly come back on again a few isolated times. And on the last try before the loud crack, it flicked off - on - off again, and then stayed off. On all these instances the start-up was perfectly normal.
Do those symptoms point to any particular problem? Could it have been the capactitor slowly failing?
Many thanks.
Bert
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On 19/09/2011 15:23, Bert Coules wrote:

Is it an electronic ballast or a conventional one? From the description it sounds as if it may be - if so then comments about PFC capacitor do not apply.
Is there a starter switch (small cylinder with two pins usually replaceable from outside)/ does it hum slightly when on? If not then it is likely an electronic ballast (a bit like a grown up CFL) with a variety of potential failure scenarios.
HTH
Chris K
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Chris K wrote:

Electronic, I think. I didn't take a note of what was printed on the module casing, but it was certainly made by MK.

No, and no.

The most urgent question in my mind is "is it safe to use the light as it stands?". Even if it is safe, if there's likely to be another general failure then I'll replace the whole thing.
Thanks for your response.
Bert
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On 19/09/2011 15:44, Bert Coules wrote:

It could just go away after cleaning the tube connectors and replacing the tubes, or it could fail completely. Electronics failure is like that... Its unlikely to fail unsafely but some varient of 'letting the smoke out' is possible.
Given the circumstances, I'd be inclined to replace it. It is possible to replace the ballasts only, eg, for twin tubes,
http://www.bltdirect.com/product.php?pid 52&cat80
but probably easier to change the whole fitting.
HTH
Chris K
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Chris,
Thanks for that, and the link. That certainly looks like the same module.

I'll check out prices and availability.

Definitely. Thanks again.
Bert
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Thanks to everyone for the helpful replies and advice. In the event, the light expired completely this evening and will be replaced completely tomorrow.
Bert
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I have only just seen this thread.
IMHO swap the lightswitch.
With all respect to your father, I believe that he may have just heard and seen what happened it the incorrect order or place.
An old lightswitch may bounce and cause a cracking sound at the switch when switching fluorescent lights. It may not even make a "full" connection when it is supposed to switch (that would explain the dead light). Add to this that fluorescent tubes do light from one end and your fathers head is closer to the switch than the light makes me believe that he heard more than he actually viewed.
If the light is controlled by two switches then swap them both.
--
Adam



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ARWadsworth wrote:

Thanks for that, and the explanation of your reasoning. But as it happens I was able to check things out for myself: I couldn't reproduce the sudden cracking sound, but I was satisfied that it was the light and not the switch which was to blame. Replacing the entire fitting confirmed this: the new unit behaved perfectly from the off and has continued to do so.

Again I understand why you might think so, but actually his hearing is considerably better than mine...
Bert
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Fair enough. After buggering about between two newsgroup providers I missed your post about swapping the light.
--
Adam



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