Fluorescent Lights: Troubleshooting and other questions

[Uriah]

Someone told me that if you leave a burned out fluorescent bulbs in
their fixture with power applied you eventually damage the fixture.
Then if you put a bulb in it will burn it out in a second.
This seems to be true from my experience. Could someone explain why
this happens and how do you test a fixture to see if it is OK before
you place a new bulb in one and risk damaging the bulb.
Thanks

 

[Phil Allison]

** A really desperate Groper.

Someone told me that if you leave a burned out fluorescent bulbs in
their fixture with power applied you eventually damage the fixture.
Then if you put a bulb in it will burn it out in a second.
This seems to be true from my experience. Could someone explain why
this happens and how do you test a fixture to see if it is OK before
you place a new bulb in one and risk damaging the bulb.

** No such test is possible.

If in doubt, replace the *starter* and use an old but functional tube to
see if all is OK.

Let it run for 24 hours before making any conclusions.




........ Phil

 

[Don Klipstein]

Someone told me that if you leave a burned out fluorescent bulbs in
their fixture with power applied you eventually damage the fixture.
Then if you put a bulb in it will burn it out in a second.

Ballast damage is unlikely but I have known it to happen. Damaged
ballasts usually make themselves known very quickly - usually by not
working at all.

More likely trouble from keeping a burned out fluorescent lamp operating
is if there is also a starter - and that can wear out the starter.

Bad bulbs are hard on starters and bad starters are hard on bulbs. But
if you replace the bulb and only the ends glow due to a bad starter, the
bulb suffers only minor to minimal damage if you pull either the bulb or
the starter upon recognizing that this is happening.
If the ends of the bulb glow *brightly* and the bulb does not start, it
gets more urgent to pull at least one. Otherwise the ballast can
overheat. Although UL testing supposedly means that the risk of a fire
starting from this is negligible or "acceptably low", I know of one
ballast that started a fire that way - in an elevator in an apartment
building that I lived in before.

If there are no starters and a replacement bulb does not start, check
for:

1. Fixture is properly grounded. This sometimes affects starting by
affecting the electric field distribution within a bulb that is trying to
start.

2. The bulb ("lamp") is of a type that the ballast is rated for.

3. Corroded connections, loose wires, etc.

After that, in my experience most likely the ballast died. And in my
experience, they die from at least mainly old age more than from
attempting to run burned out bulbs. They are designed to not die from
burnouts occurring when it will be many hours or days before maintenance
workers do anything. Any ballast manufacturer designing a ballast likely
to be used in commercial buildings I consider incompetent if the ballast
is unable to survive working with a burned out bulb for months.

- Don Klipstein ([email protected])

 

[Uriah]

Thanks for the insights. I didn't realize that the glowing ends of the
bulb, which I have seen many times, spelled failure. That will save me
quite a bit in the coming years so I appreciate the info.

Arcade games have a small fluorescent fixture in them and sometimes
these games sit in locations for years with the bulb burned out. When
I would go to replace the bulb the new one would just not start at all
and then when I would try and place the same bulb in a new fixture it
would also be dead. Can you measure the voltage on the fixture to
check and see if it is within specs? What would you look for? Or can
you with the power off check the ballast with the OHM settings on a DVM
to see if there are shorts? And the same with the starter, is there a
way to check it to see if it is the culprit? And... I am sorry about
all of the questions but I have been meaning to fill in this missing
knowlege for quite some time, how do you check a bulb to see if it is
ok? Is putting it in a known working fixture the only way?

I was working on a regular fluorescent fixture that lit a display
counter in a store . When I placed a bulb in the fixture it lit up and
I thought it was fine but it went out within a minute and when I
touched the bulb it was really hot. There was no starter on this
fixture. I don't know much about these things. What might have been
happening with this one? And like in my above question can you check
it with a DVM to see if it is OK before inserting the bulb? The bulb
costs almost as much as the fixture.

Thanks for the help I really appreciate it.

Uriah

 

[[email protected]]

Any ballast manufacturer designing a ballast likely
to be used in commercial buildings I consider incompetent if the ballast
is unable to survive working with a burned out bulb for months.

Yep - actually, theoretically a fluorescent tube doesn't have
resistance (more than a piece of wire has), it just causes some voltage
drop. So virtually, the ballast should survive from driving as shorted
as well...

For OP: It isn't virtually possible. Of course it is, but it's very
unlikely - just like the Don said (ballast damage). When a tube is
burned out, just replace it and try, if it starts, it's ok, if not,
replace the starter, then it should be ok

 

[Don Klipstein]

Thanks for the insights. I didn't realize that the glowing ends of the
bulb, which I have seen many times, spelled failure. That will save me
quite a bit in the coming years so I appreciate the info.

Arcade games have a small fluorescent fixture in them and sometimes
these games sit in locations for years with the bulb burned out. When
I would go to replace the bulb the new one would just not start at all
and then when I would try and place the same bulb in a new fixture it
would also be dead.

Makes me think the starter is stuck shorted and the ballast is shorted.

Assuming that what you have is likewhat I had when I owned an arcade
game...

However, I would think that a fluorescent lamp burning out instantly
from this would produce some sort of flash of light at the ends.

Can you measure the voltage on the fixture to
check and see if it is within specs?

If you have a 2-lead ballast, voltage will not tell the whole story. To
check the condition of a ballast in a 14, 15, 20 or 22 watt 120V
fluorescent fixture with a starter and a 2-lead ballast: Rig up a 120V
40W or 60W incandescent lamp from one lead of one "lampholder" ("socket")
to one lead of the other - using the leads other than the ones going to
the starter.
If the incandescent does not glow at all, you have an open ballast or a
broken connection. If the incandescent glows at noticeably reduced
brightness, then the ballast is almost certainly good. If the
incandescent glows at full or nearly full brightness, then the ballast is
shorted.

What would you look for? Or can
you with the power off check the ballast with the OHM settings on a DVM
to see if there are shorts?

Compare to a normal ballast of the same type and wattage. However, a
short across part of a winding can make a minor decrease in DC resistance
and a major decrease in impedance at 60 Hz.

And the same with the starter, is there a
way to check it to see if it is the culprit?

Starters should read open. But if it was used with a lamp that failed,
then it should be replaced - especially if the lamp has failed beyond
blinking or has spent a long time blinking.

I was working on a regular fluorescent fixture that lit a display
counter in a store . When I placed a bulb in the fixture it lit up and
I thought it was fine but it went out within a minute and when I
touched the bulb it was really hot. There was no starter on this
fixture.

Most likely you used the wrong bulb for the ballast being used, such as
a regular 40 watt 4-footer with a VHO, SHO or HO ballast.

Second most likely is a failed ballast where the current limiting
element is mainly a capacitor and the capacitor shorted. I saw one of
those, but lamp life was shortened only to something like several hundred
or about a thousand hours. Or you have a separate transformer and
inductor with the inductor shorted - rare except in systems ported from
one line voltage to another.

- Don Klipstein ([email protected])

 

[Uriah]

Don,

Thanks for explaining all of that to me. I am going to print out and
keep it in my Arcade Repair book as a reference for the future. I have
always wondered about this things and now I finally know.

Thanks
Uriah

 

[Don Klipstein]

Don,

Thanks for explaining all of that to me. I am going to print out and
keep it in my Arcade Repair book as a reference for the future. I have
always wondered about this things and now I finally know.

Thanks!

But I forgot something:

When I said a good starter reads open on an ohmmeter, I did not mean
that a starter that reads open is good. Only that one that does not read
open (usually shorted) is definitely bad.
This applies for the usual "glow switch" starters.

- Don Klipstein ([email protected])