Andrew Gabriel
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 Posted: Fri Aug 01, 2008 6:10 am Post subject: Ballast failures |
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Some months back, the issue of electronic ballast reliability came up,
and I said we lose quite a few at work. Yesterday, I got talking with
the engineer who replaces them all. He has a box of the failed ones
which he opens out of curiosity to see what went. We rummaged through
them, and the most common failure by far (75%) was not one I had
expected at all. It is that the PCB tracks have flashed over on the
circuit board. This seems to happen in a variety of different places
on the circuit boards. Perhaps a third of them are around the bridge
rectifier diodes, but the others are all in different places, and
not necessarily anywhere near the mains side of the circuit.
Initially I though it might be a short to the case through the plastic
insulator film all the ballasts wrap around the circuit board, but I
took several of them out and the plastic is undamaged and the arcing
hasn>t gone to the metal case - it>s between tracks on the PCB.
There are several different makes and models of ballast, all
similarly affected. They are around 6 years old. We lose around 2/week.
The second most common is a burned out component on the board, either
a non-polarised capacitor on the output side or the transformer
itself.
In a small number of cases, there is no physical damage visible.
There are also lights in the building with magnetic ballasts.
None of those has ever failed.
--
Andrew Gabriel
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