Author Topic: Flouro Ballast Failure  (Read 2401 times)
lightingcollector84
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Flouro Ballast Failure « on: April 27, 2009, 09:00:06 AM » Author: lightingcollector84
What do these ballasts typically do upon end of life?  The reason I ask is because at school I have seen 3 different ballasts do 3 different things.  We have those the just shut off and do nothing.  We have a couple that runs the bulbs, but at like half power and they flicker.  And we have a third kind that continuely flash the lights on and off for awhile and make a buzzing noise, before staying on. I'm assuming these are electronic ballasts, but I'm not 100% sure. The lamps are T8's.
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TudorWhiz
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Re: Flouro Ballast Failure « Reply #1 on: April 27, 2009, 09:54:20 AM » Author: TudorWhiz
for electronic ballasts, it can be random,

 I've seen some just stay dim,

while others just simply turn on like a rapid start fluorescent, then there's those that goes on,

but then out of no where it flickers dimming down to off, then stays off for a few min then flickers back on

Then there's those that just simply don't go on....

I believe there's some that just keeps the end glowing, but sometimes thats just the lamps....


Magnetic varies too, like it just makes ends glow...then there's those that when flipped on it just flickers but doesn't go on....

Also there's those that really EXPLODES or CATCHES FIRE! That probably is from the cap!

A ballast failure seems very common on BU40T12 (correct me if my ordering code is wrong, but its the 40 watt U shaped T12 lamps) the rapid start failure pretty common, but also it is very sensitive sometimes cleaning lamps and making sure ground is good makes it work again!
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sss2008
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Re: Flouro Ballast Failure « Reply #2 on: April 27, 2009, 10:18:58 AM » Author: sss2008
At my school I've seen some fluorescents (T8 instant start) just flash constantly and never do anything else (basically acting like a strobe light). One in my school's cafeteria has been doing this for a while now, and the lamps are extremely worn and it flashes very dim now. Another light in that same cafeteria just started doing the same thing just recently.

I've seen another T8 fluorescent fixture with a dying ballast show similar behavior, but it worked properly most of the time. Every now and then it would flash constantly the same way the other lights I was talking about did, for a minute or two. It killed the lamps within a few weeks.
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Medved
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Re: Flouro Ballast Failure « Reply #3 on: April 27, 2009, 02:36:03 PM » Author: Medved
Most of unprotected ballasts burn out after lamp EOL nearly completely (transistors + resonant capacitor + rectifier + some passives, sometimes the output ballasting inductor). Consequence is blowed fuse and/or smoke from the ballast. Repairable practically only for an enthusiast, in professional environment it's not economical to do so - you could easily spend a hour, without the warranty of success for one piece, unless only one or two components fail and such failure mode is typical for given model (e.g. transistors and fuse)...
On these it's better to use long life bulbs (those 75+khours), as with each lamp EOL it's a gamble, if and what will fail again.

Ballast operated in hot environment (too tight and/or poorly ventilated fixture,...) usually fail with dried-out capacitor(s) - depend on design, sometimes they only run the lamp dim, or flicker (50/60Hz). With a bit of luck, it does not cause any further damage, so quite easy to repair, if replacement capacitors are available... Make sense on more expensive (and protected) ballasts running 24/7 in hot environment (where the capacitor life is spent way much sooner then the rest of the fixture).

I've seen lot of electronics for electrical installation (ballasts, RCD's, motor protectors) with broken track on the PCB around the connector and/or other mechanically stressed joint (heavier coil, some component on heatsink,...). With a bit of luck, it does not cause any further damage, so quite easy to repair... But take some time to find the place...
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lightingcollector84
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Re: Flouro Ballast Failure « Reply #4 on: April 29, 2009, 07:51:18 AM » Author: lightingcollector84
What do you mean by flash constantly, does the bulb turn off and on again?  If so I know what you are talking about as we had 5 here to that exact same thing.  These were dimmable ballasts, which I think may have caused them to behave this way.
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Medved
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Re: Flouro Ballast Failure « Reply #5 on: April 29, 2009, 03:49:36 PM » Author: Medved
Dimmable ballast might start to "cycle", when at low setting.
Ballasts, what allow deep dimming levels, use some kind of close loop ionisation level regulation (as ionisation level demonstrate electrically itself as the lamp impedance and is proportional to the lamp output), what might become unstable with some (worn-out) lamps, so it start to oscillate (lamp extinguish => no ionisation => controller reduce frequency => lamp ignite => ionisation increase too much => controller increase frequency too much => lamp extinguish).
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sss2008
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Re: Flouro Ballast Failure « Reply #6 on: April 29, 2009, 06:18:58 PM » Author: sss2008
What do you mean by flash constantly, does the bulb turn off and on again?
Basically, but it happens really fast, if you blink your eyes constantly that's basically what it's doing. And it's not a dimmable ballast.

Also, the light that just recently started doing this in my school cafeteria doesn't do this now; the outer two lamps just glow red at one half and the middle lamp does nothing at all.
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Re: Flouro Ballast Failure « Reply #7 on: April 30, 2009, 09:58:26 PM » Author: Patrick
I've noticed faulty rapid start ballasts that don't reliably start lamps, probably due to bad heater windings.  In this case good lamps typically remain dim, but may eventually start up and reach full brightness.  Once lit, they'll work properly until the fixture is shut off.  There appear to be no adverse affects once the lamps are on, but the slow starting wears them out sooner.  In my parents' house there was a fixture in the basement with this problem.  Interestingly, if the light had been turned off for hours, it would start up quickly most of the time.  However, if it had been off for only a few minutes and I switched it on, the lamps would almost always remain dim.  It worked better when cold, for some reason.
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Re: Flouro Ballast Failure « Reply #8 on: May 01, 2009, 02:19:28 AM » Author: Medved
Heat expansion cause the problem to appear - it might be loose connection and/or scratched insulation. The problem might even not be directly in the ballast, but in some connection point to the lamp (socket, wire nuts,...).
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Re: Flouro Ballast Failure « Reply #9 on: May 01, 2009, 08:17:45 PM » Author: don93s
Most starting problems with RS...when both lamps are dim and start slow or not at all, result from bad wire connections to the sockets. The way sockets are designed in most cases is unreliable for good connection once the copper wire/brass has corroded inside. I fight with this all the time. Sometimes twisting the lamps back and forth will help, other times you need to remove power, take the fixture apart, and check to make sure all wires are locked into sockets, or re-strip wires and get better sockets.
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