Lights stopped working - help!

[Rob]

Hi,

Electrics are supposed to be simple. but perhaps it's me who is simple.

We have a light fitting in the kitchen with 4 halogen bulbs. It is controlled by 2 switches in parallel - one normal and one dimmer. It's been working fine - every so often a bulb goes, trips the RCD, gets replaced, and all continues working.

This time when one blew, it tripped the RCD, I reset the RCD and now the light doesn't work at all. All other lights on the circuit work OK. I have tightened all the wiring in the switches, and also the fitting. A multimeter across the two contacts in each bulb housing shows there is 240V getting to each one when the switch is on. I have replaced every bulb with brand new ones. But still no light.

I have no idea where to go from here - surely if power is getting to the bulbs then there can't be a wiring issue? Having said that I don't know if the fact there's 240V there means there's enough *power* there. I also noted that when the switch is off there is still about

25V across the contacts, but have no idea if this is normal.

Any ideas gratefully received

regards

-Rob

[The3rd Earl Of Derby]

Maybe the contacts on that particular fitting has aquired a carbon deposit build up on it and if so this would in effect trip the RCD when a lamp is replaced?

-- Sir Benjamin Middlethwaite

[Andrew Gabriel]

I suspect you mean MCB?

Multi-meters are not good for measuring mains voltage. A tiny capacitive leakage in a length of cable can result in mains voltage readings, when there is in fact no connection at all.

I suspect the lamp which failed arced across, drawing high current, and blew the dimmer (after all, it tripped the MCB instantly, which probably means it passed over 30A momentarily). It might have only blown a fuse in the dimmer, but IME it is likely to have blown the triac (the key semi-conductor component).

[Rob]

Give that man a prize. I swapped the dimmer for another one, and sure enough it worked. The coil (inductor?) on the orig dimmer was blackened. I thought the MCB would have tripped before the dimmer had a chance to blow, but there ya go.

Thanks

-Rob

[Lurch]

On or around Sat, 05 Nov 2005 16:16:48 GMT, Rob mused:

It would appear it did, several times.