Failed lamps burns out ballasts?

[mdshunk]

I did a service call last week at a location that had a few dozen metal halide outdoor lights (RAB fixtures) that were not lighting. These fixtures were not that old; perhaps 5 years or less. In each case (except one) the fixture not only had a failed lamp, but the ballast was bad and visibly burned.

This troubled me, so I checked the ballast manufacturer's webste (Venture Lighting). The technical information on the webisite caused me to believe that if a failed lamp is left in a fixture for an extended period of time, the constant "pulsing" of high voltage will break down the insulation of the ballast windings, causing them to short out.

Do others of you know this to be true? If it is true, does this also hold true for other HID types? What about fluorescents? How long is the window between the time the lamp fails, and when the ballast might self-destruct from trying to lamp up a failed lamp?

 

[mhulbert]

Re: Failed lamps burns out ballasts?

I know electronic ballasts for MH and flourescent have what's called EOL protection, which stops powering the lamp when it is dead. I'm sure it tries once each time it is energized, but this is not like a magnetic MH ballast that will keep trying.