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Strange Light Bulb Problem

J

John Sigler

Jan 1, 1970
0
Well maybe it is not so strange.

My mother has a fixture over her breakfast table which has 5 flame
shaped bulbs, wattage unknown. When one of these went out recently I
purchased package of 2 Sylvania 40 watt Flame Shape Iridescent Light
Bulbs F15. The package says it has a Safety Circuit. The base of the
bulb fits the fixture socket perfectly but neither bulb will illuminate.
If I move one of the other existing bulbs to that socket, it works
fine. There must be some problem with the bulbs that I purchased.

Other than not being tinted as darkly, the bulbs I purchased have a
different type of filament. They have a single fairly thick horizontal
filament while the bulb that I am trying to replace has a much finer
filament which is in the shape of a "C" laying horizontal and supported
at 3 spots.

Would the difference in the filament explain why the new bulbs won't
light up in that fixture?

Does the wattage matter? There are also similar 20 watt bulbs
available.

The bulbs that I purchased work in a conventional lamp.
 
V

Victor Roberts

Jan 1, 1970
0
Well maybe it is not so strange.

My mother has a fixture over her breakfast table which has 5 flame
shaped bulbs, wattage unknown. When one of these went out recently I
purchased package of 2 Sylvania 40 watt Flame Shape Iridescent Light
Bulbs F15. The package says it has a Safety Circuit.

Probably nothing more than the series fuse wire used in
almost all incandescent lamps.
The base of the
bulb fits the fixture socket perfectly but neither bulb will illuminate.
If I move one of the other existing bulbs to that socket, it works
fine. There must be some problem with the bulbs that I purchased.

Other than not being tinted as darkly, the bulbs I purchased have a
different type of filament. They have a single fairly thick horizontal
filament while the bulb that I am trying to replace has a much finer
filament which is in the shape of a "C" laying horizontal and supported
at 3 spots.

Would the difference in the filament explain why the new bulbs won't
light up in that fixture?

It shouldn't, as long as all the sockets are wired in
parallel, which seems to be the case since the other lamps
were operating even when one was burned out. The different
filament shape is due to the higher wattage.
Does the wattage matter? There are also similar 20 watt bulbs
available.

The wattage shouldn't matter.
The bulbs that I purchased work in a conventional lamp.

Are you sure that the new lamp really fits into the sockets
in the original fixture? Specifically, is the bulb portion
resting on the top of the socket and preventing the base
from fully seating in the socket and making contact with the
center pin at the bottom of the socket?

--
Vic Roberts
http://www.RobertsResearchInc.com
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P

Paul Hovnanian P.E.

Jan 1, 1970
0
John said:
Well maybe it is not so strange.

My mother has a fixture over her breakfast table which has 5 flame
shaped bulbs, wattage unknown. When one of these went out recently I
purchased package of 2 Sylvania 40 watt Flame Shape Iridescent Light
Bulbs F15.

These are just fancy incandescent bulbs, right? Not those flickering
neon bulbs.
The package says it has a Safety Circuit. The base of the
bulb fits the fixture socket perfectly but neither bulb will illuminate.
If I move one of the other existing bulbs to that socket, it works
fine. There must be some problem with the bulbs that I purchased.

Other than not being tinted as darkly, the bulbs I purchased have a
different type of filament. They have a single fairly thick horizontal
filament while the bulb that I am trying to replace has a much finer
filament which is in the shape of a "C" laying horizontal and supported
at 3 spots.

Would the difference in the filament explain why the new bulbs won't
light up in that fixture?

Does the wattage matter? There are also similar 20 watt bulbs
available.

The bulbs that I purchased work in a conventional lamp.

So, it appears that the new bulbs work and the sockets work. Right?

Hold one of the new bulbs up next to an old style and see if the threads
are the same depth. The old ones may be non standard and the new ones
won't reach the center contact in the lamp socket.

Just a guess.
 
J

James Hooker

Jan 1, 1970
0
Seen this one before! If it's not what Vic already suggested, it could be
due to the following curious problem.

These bulbs have maybe originated from a particular Asian supplier whose
shape of the metal screw base does not conform to IEC dimensional standards.
Right at the end of the screw-threaded base it should be slightly rounded.
But from this supplier it is too flat. When you screw these bulbs into the
socket, the top solder contact on the end of the base first makes contact
with its terminal in the holder, and prevents you screwing the bulb in any
deeper. But because the metal shell of the base is not rounded enough, it
fails to reach its terminal inside the holder. No contact is made and the
lamp will not light.

This problem only affects certain lampholders of a particular design, which
have their contacts arranged differently than normal (making contact right
at the end of the screw-threaded base shell, rather than on the lower side
of the base). This explains why these apparently defective bulbs work in a
different fixture.

You have 2 solutions :

1) take the bulbs back to the store and complain about it, this is the only
way these suppliers might get the message and source from a decent supplier!
When buying new lamps its best to get some from a different country of
origin, because Philips is frequently also buying its lamps in from the same
manufacturer that OsramSylvania uses.

2) after shutting off the power to the fixture, slightly bend upwards the
terminal which makes contact with the metal shell of the cap. This will
increase its chances of making contact with the malformed bases of these new
bulbs. But make absolutely sure that the power is definitely off before you
stick anything into the socket and attempt to do this!

James.
 
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