1

The light fitting in my utility room is a 5' fluorescent tube, and it's stopped working. It's about 7 years old, with a quick starting electronic ballast. The failure has been a little odd - a completely dark tube for several days whenever I instinctively tried to turn it on, then it worked for a bit, then yesterday it came on for less than a second and went off again.

I don't want to buy a tube just for testing - if the ballast is gone I'm stuck with a large fragile thing to store, and will probably end up replacing the whole fitting with something that takes LED bulbs. My only other fluorescent tube fitting is 6', so borrowing the tube out of that isn't an option.

I do have a few multimeters, and I'm used to working with mains, but don't know what to look for.

3
  • Another, off-topic, reason not to buy a tube for troubleshooting - I'd have to drive an extra trip in the opposite direction to anywhere I normally go, and I'm trying to drive as little as possible (about one trip per fortnight at the moment)
    – Chris H
    Nov 19, 2021 at 9:19
  • Get another tube and try it. If it works you're good, it not, then it's something else like the ballast. If you don't want to buy another tube I believe there are "ballast test units" on the market but I think you will find these are significantly more expensive than a tube. milwaukeetool.com/Products/Instruments/Lighting-Testers/2210-20
    – jwh20
    Nov 19, 2021 at 11:37
  • @jwh20 as I said, I'm not inclined to buy something that will probably be thrown out (it would even need a special trip to dispose of a tube). With that tester, are you implying that testing is impossible with ordinary test kit, or just stating that a convenient but expensive tool exists?
    – Chris H
    Nov 19, 2021 at 13:13

2 Answers 2

1

I wouldn't guarantee this to be a foolproof method, but as you have three potential fail-points [assuming you checked the power] & as it's a bit scary to test these things with a multimeter, then I'd start with…

This all assumes you have standard tubes with a slot-in starter, not something 'smart' like a T4 or T5 where it's built into the fitting itself

How dark is the tube at the ends? Tired old tubes can get almost black at the ends. They will also start to stress your starter, needing several attempts to fire up, before they eventually fail.
They also sometimes have a period where they will not glow so well as when they were new, or they can flicker without needing restarting - this would be sign they were leaking, so not always a symptom.

Try a new starter first - they're cheap & easy to store. if the starter is banging away at the tube with no joy, then we're back to it being the tube; but bad tubes wear out starters fast, so it's always wise the change a starter when changing a tube, & always wise to try a new starter before blaming the tube.

If no joy with either of the above, it still could be the tube… but it could be the ballast. You now have to weigh up whether you're going to risk a new tube to find out it's the ballast.

6
  • With an electronic ballast it doesn't have a starter, but I'll certainly check the ends.
    – Chris H
    Nov 19, 2021 at 12:33
  • Ah, so it is 'smart'. I haven't done fluo-tubes in a year or three, but I used to hate those things. Pretty much had to swap out the entire fitting if anything started to go wrong, though we were looking at overall cost-efficiency rather than simple one-off economy.. [I'm sure I've mentioned on here previously my experiences with thousands of T4s… never want to see one of those things ever again ;)
    – Tetsujin
    Nov 19, 2021 at 12:35
  • I've changed the ballast in the one in my garage, and it's a real pain - hence why I'll change the fitting if it comes to it
    – Chris H
    Nov 19, 2021 at 12:37
  • tbh with a 'smart' fitting I'd be tempted at this point to cut your losses & go LED. My kitchen lighting used to be all T4 [cough, wonder where I got those from] but I dumped them all for 12v LED a few years ago now.
    – Tetsujin
    Nov 19, 2021 at 12:37
  • 1
    I can't make the call for you, but new fluo, couple to 5 years. New LED, 25 years if you choose wisely. Cost, not much different… except for the can of paint ;)
    – Tetsujin
    Nov 19, 2021 at 12:41
1

I am the biggest supporter of Real Fluorescent that you will ever meet. Fluorescent technology has dramatically improved in the last 20 years, and I strongly feel that the standard 4 foot tubes are the best light available with 90 CRI readily available and 98 CRI available... far more reliable since you can get Tier 1 vendors like GE and Sylvania very affordably (the field isn't glutted with cheap Cheese junk like LEDs are). and cost actually less overall. They are not as efficient, though, so will burn more energy.

That said, anytime I am dealing with an oddball size of fluorescent, I will either go to the standard 4’ or switch to LED. The lamps are too costly when they are odd sizes.

That said, if you pay careful attention to your ballast specifications, you may be able to borrow a ballast from another fixture to try in this one. While tubes are particular to one fixture, ballasts typically work with a range of tube lengths. The ballast labeling will state the most common sizes they work with, and their spec sheet (on the Web) will list every single size they work with. Follow the wiring instructions on the label, as these differ "instant-start" vs "rapid or programmed start".

1
  • 1
    I'm sure I could swap in the ballast from the 6' fitting in the garage, as I replaced the original with a versatile one (it was a pain, different hole pattern but I realised a little late)
    – Chris H
    Nov 20, 2021 at 20:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.