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Lights flicker at first, then fine

Postby robmeister » Wed Nov 24, 2010 5:53 pm


Hope someone can help with this. I'll keep it as short as possible.

The problem: Last night, after 3 years with no problems, my study lights (2 halogen bulbs running off the same switch) initially flickered for about 2 seconds, then came on fine. Last night, I switched off for about a minute then switched on again they came on fine first time. Switched off overnight. This morning - tried again and same thing happened - initial flickering then fine ever since.

So far as I know, they run off a transformer in the ceiling space. I did have trouble with them about 3 years ago but replaced both the transformer and the dimmer switch for a simple off/on and no problems up to yesterday.

Any ideas what might be causing the initial flicker then all is well?

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Simply Build It

Postby stoneyboy » Thu Nov 25, 2010 11:39 pm

A loose connection check all before they get too hot causing burning.
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Postby ericmark » Fri Nov 26, 2010 4:11 pm

There are a number of points the first is the halogen lamp should not be connected through a dimmer unit. The whole idea is that the quartz envelope is so hot that any tungsten which lands on it is repelled and subsequently will be re-deposited onto the element. As a result running cold will reduce the bulb life.

The element is in the form of a coil and as such it will have a resonant frequency and the inverter has to match this. Also the dimmer will also have a frequency which the inverter also needs to allow for. It is rather hit and miss as to if all the components match and often I have just changed make of lamp and all sorts of odd faults have disappeared.

Capacitors have limited life and they will degrade over time so what was matched 3 years ago may over time become a miss match.

I know we do dim the quartz halogen tungsten lamp but when we do we have to accept that we are placing strains on the components for which they were not designed and premature failure is only to be expected.

The so called transformer is not that simple it is an inverter and it turns the AC supply to DC then stores it in a capacitor then turns it back to AC at a much higher frequency. At this high frequency only a very small transformer is required and the output voltage is monitored within the unit and the parameters changed to maintain the volts output to very close limits so the element temperature is maintained at the best for light output and unit life. Adding a dimmer of course completely upsets this system so no wonder it acts odd from time to time.
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