intermittent fluorescent -- kinda long

[jim evans]

I have an intermittent florescent fixture that's been plaguing me for several years. It behaves in an odd way. It's a dual 40 watt (4 ft) bulb unit. At first I replaced the bulbs 3-4 times in about 8 years. Then replacing the bulbs didn't fix it so I replaced the ballast. That worked for about a year then it began giving bad bulb signals and I replaced the bulbs again. Since then (one year old ballast and new bulbs) it's come on fine sometimes and not other times. It seems random with it not working more times than it works. When it doesn't come on the bulbs are dimly lit like failing bulbs. I tried changing the bulbs with a pair from another fixture that I new were working, no change.

It's been this way for about 5 years, so I changed the ballast again. The behavior is still the same. When I first turned it on after changing the ballast it worked fine. I turned it off, then turned it back on within a minute -- it was dim. When it's not working right, turning it off and on doesn't seem to have any effect. When it is working turning it off seems to make it stop working.

Here are some facts.

o When the bulbs are dim they are both dim but one is obviously dimmer than the other.

o I have twisted the bulbs around in the contacts many times to no effect.

o The current bulbs have this information on them [But, I've had 3 different new bulb pairs perform the same way]:

Phillips F40T12/Home Light Cool (Capital E in a circle)

40 Watt USA 7J

o The ballast information is:

Brand: Advance Class P Type 1 Outdoor High Power Factor Sound Rated A Rapid Start Lamps

120 Volts, .73 Amps

This ballast was bought at an electric supply house and it was the best one they sold.

The resistance between the two pins on the same end of each bulb is 1 ohm on both bulbs (4 pairs). From the pin on one end to the pin on the same position on the other end is open (infinite ohms) for all 4 pairs.

-------------------------------------------- 38v || fixture || 40v 38v || || 40v --------------------------------------------

These measurements were made with the bulbs removed.

View above text sketch in fixed pitch font.

jim ___ Have a home upkeep question? Try my help page. It's sort of an alt.home.repair FAQ.

[donald girod]

If you have replaced the ballast and bulbs a couple of times, it is obviously not the ballast or the bulbs. There are only three components here: ballast, bulbs, and sockets. Therefore, you probably have bad sockets, or maybe only one. There could be a bad crimp connection where the wires go into the sockets, or the socket could be corroded (doubtful). I am puzzled as to why you didn't just replace the fixture? Depending on what it is, the fixture could be cheaper than a ballast. You can get dual-40 surface mount fixtures for about $20, for instance.

Another very remote possibility is that you have like 15 fluorescent fixtures strung together on the same circuit and they are interacting with each other. When you have large numbers of ballasts, you have to do something special to keep them from screwing up--they can cause phase shift and mess up the power factor (whatever that means).

[jim evans]

Thanks for your reply. I removed and reconnected the wires at the lampholders (what you called sockets) early today -- still no help.

This is in the living room and we are expecting guests tomorrow. The wife was on my case to clean up the mess, so I went to the Borg and bought a new fixture for $14, installed it and the problem appears to be fixed (with intermittent problems it's hard to be sure).

To answer your question -- I didn't replace the fixture before earlier because I wanted a better quality ballast and new fixtures often come with inferior ballasts. I kept thinking it had to be something simple that would become obvious soon. When that didn't happen it became a puzzle. Also, this fixture's located where it's a bitch to remove and replace.

jim

[Chuck]

a 4' cool white fluorescent fixture in your living room? That's a new one.

[JM]

quoting:

Philips' fluorescent bulbs are "low mercury" types. They reduced the amount of mercury inside to save the environment. One of the common failure modes of low mercury bulbs is that they actually run out of mercury long before when they should normally burn out. This is called "mercury starvation". Mercury starvation was traditionally quite rare, but today with low mercury bulbs commonly on the market, it happens much more frequently.

The symptoms you describe sounds like mercury starvation. The other possibility is improper electrode activation. Improper electrode activation also causes the bulbs not to light, only dim. With improper electrode activation, the electrodes essentially block electricity with a high resistance electrical path through them. The bulbs will not light unless they receive a high voltage pulse, in which the ballast is incapable of.

If either is the case, the bulbs are defective. Bring them back to the store (usually orange box) where you got them from. Try to get "kitchen & bath ultra" from GE, or one of the warm white varients from Sylvania. They are not low mercury types, so they will not be prone to mercury starvation. They are often higher in quality anyways, and they will provide a warm appearance which will look better in a living room.