Where is my problem with this flourescent lamp?

[Peter]

I've got a "no-name" clamp-on fluorescent lamp that no longer starts when the rocker switch is snapped from the off to the on position. The lamp has a polarized plug with an in-line black "brick" 7 1/2" x 2 1/2" x 1 3/8" that has the code "G0138" stamped above the code "GG10051F" on the bottom but no other markings. The 2 conductor cord from the brick goes to the base of the lamp where the clamp is located. The lamp uses a single 18W 4 pin double tube bulb with code G24q-2.

I'm sure that the bulb is good because I have a second, identical lamp (that works normally) and when I swap the bulbs, the "good" lamp works perfectly with the bulb from the lamp that is not working. I also have a brand new spare bulb that I've tried in the non-functional fixture and it too fails to light in the bad fixture.

The problem started spontaneously with no earlier indication of problems. Normally, when the lamp is turned on, there are a few quick white flashes in the bulb and the bulb lights and glows steadily. The behavior I observe is that when I snap the rocker switch to on, the bulb either has one quick white flash but then I only see the heaters glowing in each of the two tubes, or there is no white flash at all, and all I see is the glow of the heater filaments. I've tried plugging the lamp into another outlet in case the problem was related to grounding (I've read that these quick start bulbs need their circuits and fixtures to be grounded to work properly) but it did not help. The "brick" has always been entirely quiet and never got particularly warm, and that has not changed.

Any suggestions (besides ditching the lamp)?

[RBM]

I think that what you're calling the "lamp", what I would call the fixture, has a bad ballast transformer. If it is integral to the fixture, it's probably not worth trying to replace.

[Peter]

Thanks for the clarification and the feedback. Yes, I was using "lamp" and "fixture" interchangeably, in distinction from the "bulb". You're right, "bulb" and "lamp" are closer in meaning; "fixture" is the entire unit from plug to bulb.

I opened the "brick"(held together by 4 small recessed screws)after sending my inquiry and it appears to contain only a ballast with 2 wires at each end (this conforms with the wiring diagram on the ballast label). The label identifies the ballast as a Fu-chi brand PC-4526P-B 300 mA for PL-C 18w. Extensive work on Google has failed to yield a useful hit for a replacement. The closest I saw had 3 output wires and no dimensions were provided.

[RBM]

That's what happens when Google gets kicked out of China. It may be possible to get a replacement from the manufacturer of the fixture, but more and more, I'm finding that approach fruitless as well.

[Pat]

If you are able to find parts they are likely to cost more than a new fixture.

[Stormin Mormon]

So, so true. It's a shame, but this is a throw away society.

[Peter]

OK, it seems unanimous here and on alt.engineering.electrical. If the problem is the ballast, I'm ditching the fixture. Used every search engine I can think of, including metabrowsers and I couldn't locate a replacement (if this were a shop light I would have an embarrassment of riches deciding where to buy). Too bad, I probably didn't use the fixture for more than about 300 hours. I think I paid about $25 for the fixture on sale at an art supply store about 3 years ago. Maybe that's why the item was on sale!

I think I'll stick to the old fashioned fixture that requires you to hold down the on button while the filaments heat up, and then release the button. Those seem to last forever (or as long as the switch does!)

[Tony]

Sounds like a standard 18 watt ballast. Just go to an electrical lighting store probably cost about $6. I bought one a few months ago at Lowes on closeout, cost me 18 cents.

[Tony]

Did you try switching the starters?

[The Daring Dufas]

It's a manual start light fixture where you push and hold a button for a second or two.

TDD

[The Daring Dufas]

OOPS! Sorry, premature postification. That's a different fixture that may actually have a starter.

TDD

[The Daring Dufas]

Someone mentioned this already and got me thinking. The older fixtures like yours have a replaceable starter that is easily accessed. For cost savings, your fixture may have a starter hard wired into the fixture itself. Turn on one of the good fixtures and listen closely the part of the fixture on either end of the lamp, if you hear a couple of clicks that may have a sound like "tink", it could be a starter. You could easily disassemble the fixture and take the guts from a standard starter and use the parts to replace what's in there. There is also the possibility that instead of a conventional starter, there could be a thermistor like what is in an old TV degaussing circuit. You won't know unless you take it apart.

TDD

[Peter]

The fixture has no starter that I could find. If I found 1, it would be the 1st thing I'd do.

[Peter]

The fixture always did start with a "tink" "tink" "tink" each one corresponding to a flash of the bulb. I don't hear that noise at all now.

I was able to pull off the rotating shade, unscrew the bulb socket, pull it out about 2", and observe a 1" glass bulb that looks almost like a neon bulb with an opaque mercury-like metallic coating on the inside of the glass bulb. There are

2 wires coming out of the base of this little bulb, 1 connected to the black, and the other to the white power wires that enter the base of the socket. Perhaps this is the hard-wired starter? There are no markings on it at all. I reattached the bulb, plugged in the fixture, and turn it on while observing the little glass bulb. Nothing at all; no glow, no sparks, no "tink" "tink" "tink". What do I replace it with?

[BQ340]

I've gutted a fluorescent starter of the required wattage to repair lamps that have them built into the fixture:

MikeB

[The Daring Dufas]

If you get a standard starter look at the contact end and if it has a aluminum can, you can bend the tabs back and remove the guts and there will be the silvered bulb with a capacitor in parallel with it. Some of the new starters are in a plastic can but you can open them too. The glow tube incorporates a switch which is normally open. When power is applied a glow discharge takes place which heats a bimetal contact. A second or so later, the contacts close providing current to the fluorescent filaments. Since the glow is extinguished, there is no longer any heating of the bimetal and the contacts open. The inductive kick generated at the instant of opening triggers the main discharge in the fluorescent tube. If the contacts open at a bad time - current near zero, there isn't enough inductive kick and the process repeats. That's the tink, tink sound you hear.

TDD

[Peter]

Can I use the glow tube from an FS-2 starter (rated for 14, 15, and 20W bulbs) or do you recommend a different standard starter? Also, my socket does not seem to be using the capacitor; I assume that I should ignore that component and just replace the defective glow tube with the new one.

[The Daring Dufas]

The capacitor is for suppressing radio interference, you can install or leave it out. Get a starter that matches the wattage of your lamp. The starters will often operate over a wide range. You can actually test the rest of the light fixture (carefully) if you briefly short across the starter wires and see if the light comes on. That's what the old style push to start fluorescent desk lamps do. You can get tiny crimp connectors form your local Radio Shack for the small wires but soldering will do.

TDD

[Tony]

Yes, an FS-2 should work fine.

[clare]

Turning the plug around makes no difference? How about grounding the fixture? Flourescent tube lamps basically require a "ground plane" to light properly - sometimes simply "stroking" the tube when you power it on will make it light.