I have a Philips fluorescent light fixture in my kitchen. It was installed in the mid-1990s, so it uses an electronic fast-start ballast. The lights were not turning on at all, so I replaced the ballast with a brand new one. I also replaced the two T12 bi-pin bulbs with new ones.

Now, the lights DO turn on but they take between 5 and 10 seconds, gradually fading in. I have the exact-same light fixture installed in other rooms of the house and they all turn on instantly.

I thought that by replacing the ballast and bulbs, it would take care of that problem, but it didn't.

What could be causing the lights to turn on slowly?

I tried searching online and the usual answer is the starter or ballast. My fixture has no starter and I already replaced the ballast.

Thanks for any help.

Here are some photos of the light fixture:

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This is the new ballast, a Philips Advance AmbiStar Ballast RELB-2S40-N, which is the same one I installed in all of my other fixtures that start instantly:

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  • Is the fixture on an ordinary toggle switch? Or something "extra" - smart, dimmer, motion sensor, timer, etc.? Apr 3, 2019 at 17:58
  • Yes, just an ordinary toggle switch .
    – GTS Joe
    Apr 3, 2019 at 18:00
  • Can you disconnect the ballast check incoming voltage with a meter? Apr 3, 2019 at 18:01
  • Sorry, I have no voltage meter. What do you think it could be?
    – GTS Joe
    Apr 3, 2019 at 18:03
  • The active parts are ballast, bulbs, starter. No starter & you've replaced ballast & bulbs. So that leaves incoming power. A smart/dimmer/sensor/timer switch could easily mess that up, but you don't have that. Which leaves the question of whether something else is messing up power, and the way to test that is with a meter. Should get ~ 120V with no load or with a small load (e.g., I would wire up a LED or incandescent bulb or a fan or radio or something). If you start at 120V and a small load drops it a lot, or if you start way below 120V then the incoming power is the problem. Which could Apr 3, 2019 at 18:07

2 Answers 2


Fluorescent tubes have 2 pins because each end isn't just an electrode, it's also a preheating filament. This helps the arc to initially strike, with less wear-and-tear on the tube (longer tube life).

You have chosen rapid-start ballasts, which start the tube after a very short delay, which is used to stretch bulb life. The other options on the menu are

  • programmed rapid-start aka programmed-start, which monitor the filaments and wait until they're fully preheated before striking... Giving much longer bulb life, but longer to start in the cold (several seconds). These are great for harsh conditions, motion sensor (frequent on/off) or hard-to-reach bulbs.
  • instant-start which ignore preheating (hence, 1 wire per end) but strain tube life.

The line between rapid-start and programmed rapid-start is blurring, and I suspect your rapid-start ballast has a little bit of "smarts". Since your environment is not cold, I suspect the problem is a broken tombstone (end lampholder) or the wire not fully/properly connecting to the tombstone. One wire is connecting, but not both, so that end cannot preheat - and the ballast knows that and is delaying start.

Most rapid-start ballasts are 2-bulb-mandatory, so a problem with either tube could prevent both from starting. So I would carefully check all your tombstone connections.

If you have a voltmeter you could also pull 1 tube and put a voltmeter between the two terminals on one end (at a time); you should see small voltage the instant power comes on, and more after. If you see 0 voltage between the terminals, that may be the source of trouble.

Tombstones are pretty standardized down to just 3-4 types. Watch that your height matches, there are 3 heights also.

As far as LED tech, I know everyone's all "Oh, just junk the fluorescents, get fancydancy LEDs!" And they want you to run down to the big-box and grab the cheap $8/tube LED conversions. The problem is, first, they're cheap stuff, whereas that ballast and those tubes are top quality product that will last. Second, right next to them in the store is 90CRI or even 98 CRI real fluorescent tubes with absolutely fantastic light quality. I use 90CRI T8s that cost less than $2 each. The LEDs can get near that, but the cheapies can't.

If you go LED, make sure to buy ballast-bypass aka direct-wire LEDs, because it's stupid to continue to use the ballast. Also get tubes that take hot and neutral on opposite ends, because those two little pins were never made for 120V. Then you simply rewire (a rapid-start fixture) all blue/red to supply hot, and all yellow to supply neutral and bypass the ballast.

  • How could the tombstones be broken? Could they maybe be worn out? Are the tombstones the lampholders, like these? homedepot.com/p/…
    – GTS Joe
    Apr 3, 2019 at 19:58
  • 1
    @GTSJoe Dead nuts correct. Watch the heights, that one looks correct. The tombstone may not be broken so much as wire not fully connected to it. Apr 3, 2019 at 20:01

A quick-start ballast works by sending two different voltages to the lamp:

  • A high-voltage (a few hundred volts), low current until the lamp "breaks over".
  • A medium voltage (~30 V) at ~1 ampere while the lamp is operating (conducting).

Likely, the old ballast was quick but inefficient; the newer ballast sacrifices startup speed for more efficient current use (phase lead/lag as well as power requirement).

You would have been better served by installing LED replacement tubes and removing the ballast entirely. LED lamps far outlast fluorescents, are more efficient, and are available in different color temperatures. They are available for US$10 or more. Note that some of these lamps take as long as a second to start, so read the reviews.

  • When I saw the question, I also thought "why not switch to LEDs". But the OP apparently has plenty of the same basic fixture, ballast, etc. and wants to keep it all the same. Your answer is good advice but doesn't answer the actual question. Apr 3, 2019 at 18:40
  • That particular bulb you linked to looks like its designed to use the ballast and not take a full 120v in a "ballast bypass" mode. Those do exist, but the one's I've seen are all from generic/small manufacturers not major national brands like so.
    – JPhi1618
    Apr 3, 2019 at 18:52
  • Would LED tubes work in the same fixture? Also, I have the same fixture in other rooms and the lights turn on instantly in the other ones.
    – GTS Joe
    Apr 3, 2019 at 19:21
  • I think you are forgetting the preheating power to the end filaments. Apr 3, 2019 at 19:30
  • @GTSJoe, check the lamp specification: some use the connector shorted, others require a wire from one end to the other. Some lamps might require new "tombstone" bi-pin sockets. Apr 3, 2019 at 22:59

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