LV electronic ballast failures for halogen

[nobledane]

Hi,
At my house i have in wall stair lights that are 20W halogens (x3). A week or so ago i switched on the 2 way switch from the bottom of the stairs and all three went at the same time. I thought it was the bulbs at first but quickly discovered they were fine. My next thought was the electronic ballasts so i pulled out the fitting and checked the AC voltage at the input terminals which measured 250V (note that the rcd/mccb did not trip when they went out) but nothing at the output terminal where there should have been 12V i believe. Hence i thought the ballasts were stuffed so i went and bought 3 new ballasts and put one in.. still nothing on the output side of the new ballast... strange.. so tried another one and still nothing on the output side of the second new ballast.. WHAT IS GOING ON? Scratching my head over this one...

Cheers,

 

[berkeman]

Hi,
At my house i have in wall stair lights that are 20W halogens (x3). A week or so ago i switched on the 2 way switch from the bottom of the stairs and all three went at the same time. I thought it was the bulbs at first but quickly discovered they were fine. My next thought was the electronic ballasts so i pulled out the fitting and checked the AC voltage at the input terminals which measured 250V (note that the rcd/mccb did not trip when they went out) but nothing at the output terminal where there should have been 12V i believe. Hence i thought the ballasts were stuffed so i went and bought 3 new ballasts and put one in.. still nothing on the output side of the new ballast... strange.. so tried another one and still nothing on the output side of the second new ballast.. WHAT IS GOING ON? Scratching my head over this one...

Cheers,

Do you still measure 250V input when you are trying to run the ballast? If there is a loose wire in the feed line (like at one of the wire nuts), the open circuit voltage could still read 250V, but as soon as you try to draw a load current, it could be dropping to some low value through the resistance of the loose wire fitting...

That would also explain why all 3 went at once.

 

[nobledane]

thanks - but yes there is still 250V when i try and run the ballast.. and it makes a humm as they usually do.. just nothing on the output of 3 different ballasts...

 

[berkeman]

thanks - but yes there is still 250V when i try and run the ballast.. and it makes a humm as they usually do.. just nothing on the output of 3 different ballasts...

Hmm. That is indeed strange. Can you wire in an incandescent bulb temporarily to see if it works? Can you try the ballasts at a different, known-good location?

Maybe they are just cheap ballasts that break easily? Can you ask the store if they get many returns on them?