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Ballast transformer?

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ant
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Username: ant

Post Number: 764
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Posted on Thursday, 03 February, 2011 - 09:58 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello all,

I have two little table lamps which use a 9W (7W? I forget) U-shaped tube, I think it's a 2D. Nice little light and very handy for how I use them. One is on all day most days and the primary of the transformer's burned out, as has the thermal fuse fitted therein. 125oC, out of interest.

Don't think cheapskate, think practical recycler with a huge junk box; I measured the (AC) output of the good transformer and it's mains voltage off load, ie with the lamp switched off, and 72v when lit. The transformer _looks_ normal and is quite substantial but still generates enough heat to discolour the psu case - how does it do it's ballasting act?

It seems daft just to ballast it with a resistor but I suspect that all it has is a thin secondary winding, would that be right?

On the other hand it'd be a darn sight easier to pop into town and buy something - this is about 14 years old. A shame, it's a nice little lamp and there's nothing wrong with the polite end!

Regards Ant
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g6osv
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Post Number: 117
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Posted on Thursday, 03 February, 2011 - 10:12 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Probably "impedance protected",it would only supply enough current for the lamp at full power.,
Ian
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dave_g
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Posted on Thursday, 03 February, 2011 - 10:16 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ant, I'm not sure about the "transformer"...

What I can tell you is I've never seen a 9w, or a 7w, 2D ever - I guess what you have is a compact fluorescent. In any event, if there are four wires from the lamp, these days no-one uses ballasts, it's all high frequency gear. It runs cool(er) and saves energy.

You might be able to replace the transformer with some HF gear (check out www.osram.co.uk) but you'll need to go to a specialist to get it, and it's probably cheaper to pay a visit to Ikea for a replacement.

They had some very nice - and cheap - LED task lamps a week or two back.
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alec_t
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Post Number: 499
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Posted on Friday, 04 February, 2011 - 01:54 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ant, I'd guess the 'ballasting act' is mainly done by the impedance presented by the transformer inductance.
By the way, we hobbyists don't have 'junk boxes'. They're 'potentially useful resource boxes'. (But I know 'er indoors wouldn't agree )

Alec

(Message edited by alec_t on 04 February, 2011)
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gordon
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Posted on Friday, 04 February, 2011 - 03:35 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I wonder if you can take the electronics out of a normal 9W compact fluorescent lamp, and use it to power the fluorescent tube in your lamp. You can pick up CFL's for pennies now, and it would be a greener solution.
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alec_t
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Posted on Friday, 04 February, 2011 - 07:05 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Good idea. I've been thinking of cannibalising a CFL to get a ballast for a small UV tube. Anyone managed to dismantle a CFL successfully?

Alec
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ant
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Posted on Friday, 04 February, 2011 - 10:05 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello all, as appropriate,

I've not investigated the name I gave it - if 2-D doesn't fit, sorry. Certainly it's a miniature fluorescent so nowadays it would be referred-to as a CFL. Wouldn't it?

This is the lamp, albeit my replacement was a Sylvania:
http://uk.farnell.com/osram/ds7827/lamp-dulux-s-internal-7w/dp/1528616

Radio amateurs have Junk Boxes! The contents, of course, are only potentially useful sometime in the future...

The transformer looks fairly conventional, even on the heavy and well-built - ie bulky, solid - side. How is it given a suitable inductance?

I'd not thought about cannibalising a working CFL, too late I've cut the cable off it and scrapped it!

I'm sure the CFLs I've investigated have merely been priseable apart, they're clipped together. Alternatively a bit of judicious hacksawing would suffice. You'd probably need to unsolder the wires at the contacts, that's what keeps it clipped together!

Regards Ant
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terrym
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Posted on Saturday, 05 February, 2011 - 02:09 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I'm glad you can get CFL's for pennies.
We are being ripped off royally here in Oz with the cheapest now around the 2.50GBP / $5AUS mark each. Have even seen some for more than double that.

Before the banning of incandescent's, we could get them for less than 50cents (~25p) each in the bargain stores.

TM
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gordon
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Posted on Saturday, 05 February, 2011 - 12:11 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Terry, you are right about the big profits being made by some CFL manufacturers. The prices range from about 20p to £5-00 in the UK, but the £5-00 lamp is not 25 times better!, although the more expensive lamp will probably last longer.

Alec, there is a good website here about the workings of various CFL lamps.

http://www.pavouk.org/hw/lamp/en_index.html
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alec_t
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Posted on Saturday, 05 February, 2011 - 04:52 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Thanks for the link.

Alec
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dave_g
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Posted on Saturday, 05 February, 2011 - 04:57 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Gents - there is a world of difference between the 20p ones in the supermarket and those you pay more for.

Life, lumen output, lumen maintenance, light quality, light colour, starting time. This is, as some will know on CZ, part of my professional life.

The very cheap lamps are subsidised by energy companies. Those at £2-£3 is probably about right for a domestic grade lamp.

Trade varieties with their vastly longer life and better performance, work from £10 to £25 per lamp.

Like anything else, choose the right thing for the job. I have a load of cheapies, because unless you are paying for labour, the more expensive ones do not make sense.

Terry - don't buy the CFLs, you can always buy the Halogen version of the incandescent lamp you used to buy (if the ranges are the same in Oz as they are in Europe).
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terrym
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Posted on Sunday, 06 February, 2011 - 04:48 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi Dave. The price difference I was referring to above was for the same ones! Probably should have made that clearer.

While I am aware (having been in business) you have to make a profit to survive,more and more businesses are just gouging the living daylights out of what ever they can, just because they can.

Afraid the Halogen range in Oz is very small. Don't forget, Oz is at least 10yrs behind the rest of the world in most things (and 20yrs if you live in South Oz).

TM
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dave_g
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Posted on Sunday, 06 February, 2011 - 07:41 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

OK, fair enough Terry! Here in the UK, the subsidies are still in full flow and these lamps sell locally for £0.10.

You should be able to get halogen versions of the old "GLS lamp" (household bulb), 30-40% less energy and a whiter, crisper light.

Here's one example:

http://www.philips.co.uk/c/other-light-bulbs/ecoclassic-53-w-70-w-normal-cap-warm-white-872790025172225/prd/
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alec_t
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Posted on Sunday, 06 February, 2011 - 01:06 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Why are the energy companies subsidising CFLs? You'd think it would be in their interest to encourage us to use more energy, not less. Presumably they get Government grants to promote energy-saving, i.e. Joe Public ends up paying!

Alec
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dave_g
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Posted on Sunday, 06 February, 2011 - 04:00 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Alec - spot on.

The other point is, of course, energy scarcity. Much cheaper to be in an Industry that has enough capacity (ours doesn't) for future needs.

Oh, and the PR value of Corporate Social Responsibility, of course.
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twintub
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Posted on Sunday, 06 February, 2011 - 09:33 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

@alec_t

The Government targeted the energy companies to save x amount of Co2 through energy initiatives. The easiest (aka cheapest) way that the energy companies could achieve the target was to issue virtually free CFL's!
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g6osv
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Posted on Sunday, 06 February, 2011 - 09:53 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

needed some 1n4007's.24p each from maplins
10p for6 if you get a 10p cfc from Asda.
Ian
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terrym
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Posted on Monday, 07 February, 2011 - 01:43 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

There are no subsidies here in Oz for CFL's or any thing else.
Power companies are supposed to give free energy audits to tell you how to save energy and give you one free cfl and one free draught excluder. Yea, like they advertise that, the CEO needs his new mercedes first .

As a ham looking at homebrew, the best way to get RF items is to strip tuners from Satellite receivers, Set-top boxes, old video's etc for parts.

TM

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