The most common cause of flickering appears to be aging. These neon
bulbs are supposed to have very long lives, so the flickering early in
the life of an appliance could be a sign of premature bulb failure. It
is probably not easy to replace these bulbs, so you may have to live
with the flickering.
The on-line article, ?Notes on the Troubleshooting and Repair of Small
Household Appliances and Power Tools,? Version 2.73, Copyright ©
1996-2005, Samuel M. Goldwasser, has undergone a number of revisions,
so the author has had an opportunity to respond to feedback about
errors. Here is what the author has to say about these bulbs:
?Neon lamps: These are very common as AC line power indicators because
they are easy to operate directly from a high voltage requiring only a
high value series resistor.
They are nearly all the characteristic orange neon color although
other colors are possible and there is a nice bright green variety
with an internal phosphor coating that can actually provide some
illumination as well. While neon bulbs do not often burn out in the
same sense as incandescent lamps, they do darken with age and may
eventually cease to light reliably so flickering of old Neon bulbs is
quite common. This is almost always just due to the natural aging
process of the indicator and does not mean the outlet or appliance
itself is bad.
Some Neon bulbs come in a miniature bayonet base. Most are soldered
directly into the circuit via wire leads.
Testing: Inspect for a blackened glass envelope. Connect to AC line
(careful - dangerous voltage) through a series 100K resistor. If glow
is weak or absent, Neon bulb is bad.?
http://www.repairfaq.org/sam/appfaq.htm#afindicate
(The quote is from the subsection, ?Indicators - incandescent or neon
light bulbs or LEDs,? within the section ?Types of Parts Found in
Small Appliances.?)
----------
Here is a quote from another site about flickering in neon night lights:
?Most of you are probably familiar with these. They usually have a C2A
(NE-2H) neon lamp and a 33K resistor. These do indeed draw 1/4 watt of
power. The NE-2H neon lamp is rated to last 20,000 hours with 120 VAC
and a 33K resistor. The neon lamp normally fails gradually, either
flickering or becoming dim instead of suddenly burning out.
The NE-2H neon lamp is also rated for use with a 22K resistor to use
1/3 of a watt. However, the life rating drops to 5,000 hours. If you
try to get really long life by hacking out the resistor and replacing
it with one over 33K or adding additional resistance, you may be
disappointed. Life increases only roughly proportionately with
resistance as resistance is increased above 33K.?
http://members.misty.com/don/nitelite.html
----------
Below are two quotes from a Google Groups site used by hobbyists. The
first quote lists another reason for flickering, but I suspect that
this applies to people designing and building their own equipment. The
second quote (by another person) states that failure of neon bulbs is
quite common. (He?s probably talking about bulbs that hobbyists
purchase, but the phenomenon could occur in commercial manufacturing
also.)
Quote 1:
?>Anyone have specifications for NE-2H (Neon Lamp)?
>Striking voltage, valley voltage, etc.? ?
Striking voltage varies so much and so wildly with age, condition,
manufacturer, etc... If it reliably strikes at 110 volts AC (peak
voltage 155 volts) in the dark I would not consider it
failed/defective. And they have some photoelectric effect!
Valley voltage: Varies widely with manufacturer, age, condition...
Anywhere from about 54 volts to 80 volts or maybe even a bit more
(well-used). I would say typically 65 volts valley voltage.
Valley current - Design for the voltage drop to be close to the
valley voltage at any current from 2.5 to 4 mA. There may even be
more than one valley in the 2 to 4 mA range. Secondary valleys
sometimes exist sometimes at somewhat lower currents. The lamp may
flicker if the current is low enough to have the electrodes not fully
or nearly fully covered with glow (the glow may jump around like it
does in "flicker flame" neon lamps) - you need the current to exceed
that of the highest-current valley to avoid that. But have current
exceeding that of the highest valley by as little as practical -
current in excess of that of the highest valley results in "abnormal
glow" or glow having "above-normal current density", and that causes
accelerated wear on the electrodes (and the bulb being darkened by
"sputtered" electrode material).
Life expectancy: At 120 volts AC, traditionally 20,000 or 25,000
hours with a 33K resistor, 5,000 hours with a 22K resistor. At 120
volts AC, a resistor of 39K or 47K usually results in current close to
the main or highest valley current - going higher extends life no more
than proportionately.
NE2H is sometimes AKA C2A. There is a mini-NE2H sometimes AKA A1C,
which is Radio Shack 272-1102, even though the catalog claims that it
is a C2A.?
Quote 2:
?Even on 240V failed neons re quite common.?
http://groups.google.com/group/sci.electronics.design/browse_thread/thread/26adcd62c93e74cc/2e91d2c1e472a4bd%232e91d2c1e472a4bd?sa=X&oi=groupsr&start=0&num=2 |
