Fluorescent Lights: Troubleshooting and other questions

** A really desperate Groper.

** 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

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 ( snipped-for-privacy@misty.com)

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

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 :-)

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.

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.

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.

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.

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 ( snipped-for-privacy@misty.com)

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

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 ( snipped-for-privacy@misty.com)