Dimmer switches

We have three dimmer switches similar to this one. http://tinyurl.com/8ulbg9m Recently two have ceased to dim. Can they be repaired rather than replaced. To a non electrician like myself the wiring on all three looks OK. One room with a four light fitting seems a bit darker than it should be as if the dimmer was not fully turned. TIA Jack
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Replace - they are usually essentially sealed units and almost impossible to repair.
Screwfix, Toolstation, or tlc-direct are your best sources.
--
Woody

harrogate three at ntlworld dot com
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Normally caused by the Triac (semi-conductor which chops the mains) being destroyed by the surge when a lamp blows at end of life. For anyone into electronics and soldering, it's easy and cheap to replace the Triac. Otherwise, you'll have to buy a new dimmer.
If the dimmer is an expensive matching wiring accessory, you might be able to find a cheaper one from the same manufacturer which uses the same dimmer module, and transplant it.
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Andrew Gabriel
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On 25/10/2012 20:47, Andrew Gabriel wrote:

Thank you, we had had several lamps blow when turning on one of the switches. Jack
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On 25/10/2012 20:47, Andrew Gabriel wrote:

I contacted the makers of the two lamps we have been using recently. Osram replied:
"The life expectancy of a conventional tungsten filament lamp is 1,000 hours (depending on supply voltage).
Mains voltage tungsten halogen lamps generally have a life expectancy of around 2,000 hours or 2 years, but this is not a guaranteed life.
Conventional tungsten filament lamps can draw a large (short term) current when the filament fails at end of life. I expect it is this which may have caused the dimmer failure.
However, we manufacture an eco version tungsten halogen lamp that has a built in fuse, which effectively cuts off the high surge current very quickly at end of life, and should therefore be a lot more beneficial for dimmer switches" Jack
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On 30/11/2012 19:42, Jack London wrote:

Once upon a time I had a dimmer switch with a built-in fuse. Now I know why.
Mind, I had a lamp go and take out the fuse on the board the other day. And I then found I didn't have a spare...
Andy
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IME, a triac blows much faster than a fuse.
On an expensive X10 DIN rail dimmer, I fitted a 3A type B MCB, in the hope this would reduce the chance of wrecking it when a lamp blew. It never did get damaged, but it's now driving 12V electronic transformers anyway where this isn't an issue.
In another circuit where I'm switching the mains using power MOSFETs, I used an FF fuse (very fast blowing), again with the hope it would protect the MOSFETs, but this is a heater load with no switchon surge.
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Andrew Gabriel
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