DIYbanter - View Single Post - Where is my problem with this flourescent lamp?

Peter[_14_]

On 4/24/2010 8:32 PM, wrote:
On Sat, 24 Apr 2010 10:32:44 -0400,
wrote:

Peter wrote:
On 4/23/2010 10:56 AM, RBM wrote:
wrote in message
...
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)?

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.

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.

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.

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.
Thanks for the suggestion. The fixture has a polarized 2 prong plug. I've got
one of those handy-dandy circuit testers with 3 neon bulbs on 1 end and a 3
prong polarized plug on the other and it tells me that the circuit I'm using for
the fixture is properly grounded. I did try making nice to the glass tube while
it was attempting to light - no change. No, I don't think grounding is the
problem. Besides, the fixture worked just fine for 3 years plugged into the
same receptacle.