buzz off

[buddha]

hello people,I recently had to return to a job my boss and I wired.

The problem being that several of the 12v downlights had stopped working,having checked for voltage and changing lamps,I changed the transformers,one 20-60w dimmable transformer for each downlight.

I had to change about 6!! the job has only been in for two years.

Whilst doing this I noticed there was between 50-70 volts being provided to the primary side of transformer even when the switch was turned off!

turning the relevant mcb off removed power completely.

In line dimmers were used,with a cat 5 going from the switch to the inline dimmer.

would the the fact that the transformers were being feed 24/7 have something to do with so many having to be replaced????

Could it be something to do with the inline dimmers fading?

Is this normal?

Is this safe?

Any advice from those with better brains than me would be much apprieciated.

all the best

oh yeah,and I forgot ,the reason for the topic title,one of the lamps/light fittings,the end of line fitting kept making a buzzing noise.

checked voltage on primary side(238v with switch on,54v with it off),changed transformer,still buzzing,even when turned off!!!

lastly I changed the lamp (12v two pin type 50w) and all was resolved,well the buzz had gone.

Just wondered why it would buzz when not turned on,why it buzzed when it was on?

 

[m4tty]

The voltage you are seeing MAY be inductance from other circuits. (cables run parallel). Digital multimeters get fooled whereas analogue meters wouldnt show this voltage. HTH

 

[Evans Electric]

I think its down to quality , most transformers seem to on the cheap and nasty side ,same with a lot of dimmers . Also with dichroic lamps, some jobs the client will say they last for ages ," Never changed A lamp since you fitted them" others lasting 3 weeks . I don't like dimmers , I think they bring problems, or those touch delay switches , never actually switch off , always leaking voltage, I tried to use one with a relay , it had melted the coil by the next day.

 

[Lurch]

Digital multimeters get fooled whereas analogue meters wouldnt show this voltage. HTH

Not all digital meters, just some.

those touch delay switches , never actually switch off , always leaking voltage, I tried to use one with a relay , it had melted the coil by the next day.

I've tried fitting CFL's and LED lamps to touch dimmers and most will just not switch off.