Weird Bulb

N

N. Thornton

Guest
Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?


Regards, NT
 
On 29 Apr 2004 16:56:27 -0700, the renowned bigcat@meeow.co.uk (N.
Thornton) wrote:

Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?
Click to expand...
On our 120VAC/60Hz, floodlights will often buzz at maybe 10-20Hz for
some time before failing. If you turn the switch off, they invariably
will not turn on again. I think the filament breaks and the magnetic
forces excite a mechanical resonance in the element, causing it to
flap back and forth, arcing as the end touches.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
In article <a7076635.0404291556.7f06aa77@posting.google.com>,
bigcat@meeow.co.uk (N. Thornton) wrote:

Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?


Regards, NT
Click to expand...
The arcing from a break in the filament is really nothing at all. It's
comparable in brightness to shorting a 9V battery.

The spectacular arcs are when the filament shorts the leads, melts the
leads, and then the leads fall on to each other. It draws enough
current to start an electric plasma fire. The best I've seen yet lasted
about 10 seconds then blew a 20A breaker. Better quality light bulbs
have a fuse wire to prevent this. It's a fire hazard.
 
"Kevin McMurtrie" <mcmurtri@dslextreme.com> wrote in message
news:mcmurtri-E493F0.21264529042004@corp-radius.supernews.com...
In article <a7076635.0404291556.7f06aa77@posting.google.com>,
bigcat@meeow.co.uk (N. Thornton) wrote:

Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?


Regards, NT

The arcing from a break in the filament is really nothing at all. It's
comparable in brightness to shorting a 9V battery.

The spectacular arcs are when the filament shorts the leads, melts the
leads, and then the leads fall on to each other. It draws enough
current to start an electric plasma fire. The best I've seen yet lasted
about 10 seconds then blew a 20A breaker. Better quality light bulbs
have a fuse wire to prevent this. It's a fire hazard.
Click to expand...
The best one I saw was on a old XL 80cc motorcycle I got running for some
friends. The ex-car head lamp turned blue when I downshifted too hard
(brakes didn't work too well) on a big hill!

I had a similar experience with a halogen bulb on my snowmobile when the
voltage regulator wire formed a bad connection, which allowed full magneto
voltage (at considerable power) to burn the bulb out and turn the light beam
to a unique purplish blue that lit all the snow up. To add insult, the bulbs
cost $15, and it fried both beams within an hour or two, while in the dark
in the middle of nowhere. It was also hard to find that bad connection, as
it came and went.
 
"Kevin McMurtrie" <mcmurtri@dslextreme.com> wrote in message
news:mcmurtri-E493F0.21264529042004@corp-radius.supernews.com...

The spectacular arcs are when the filament shorts the leads, melts the
leads, and then the leads fall on to each other.
Click to expand...
I can do Better - I once stuck a Mercury high-pressure lamp into a standard
socket because - "if it goes in there it's supposes to work like that" ;-)

This thing lit up like a Neutron Bomb before the fuses popped - I though I
had gone blind and everyone was falling over furniture etc. Was great fun
though - afterwards, sortof 15 minutes later when the eyesight came back so
we could change the fuses.
 
Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote in message news:<tg63905astlh5hkq72uuuvjcuu8mn80jh1@4ax.com>...
On 29 Apr 2004 16:56:27 -0700, the renowned bigcat@meeow.co.uk (N.
Thornton) wrote:

Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?

On our 120VAC/60Hz, floodlights will often buzz at maybe 10-20Hz for
some time before failing. If you turn the switch off, they invariably
will not turn on again. I think the filament breaks and the magnetic
forces excite a mechanical resonance in the element, causing it to
flap back and forth, arcing as the end touches.


Best regards,
Spehro Pefhany
Click to expand...
That would explain a lot. I guess I was just surprised that it would
arc for so long without either the filament end burning away or the
arc growing and bypassing the filament, and ending things quickly.

Thanks, NT
 
On Thu, 29 Apr 2004 21:26:45 -0700, Kevin McMurtrie
<mcmurtri@dslextreme.com> wrote:

In article <a7076635.0404291556.7f06aa77@posting.google.com>,
bigcat@meeow.co.uk (N. Thornton) wrote:

Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?


Regards, NT

The arcing from a break in the filament is really nothing at all. It's
comparable in brightness to shorting a 9V battery.

The spectacular arcs are when the filament shorts the leads, melts the
leads, and then the leads fall on to each other. It draws enough
current to start an electric plasma fire. The best I've seen yet lasted
about 10 seconds then blew a 20A breaker. Better quality light bulbs
have a fuse wire to prevent this. It's a fire hazard.
Click to expand...
Every few months I have a light bulb go with a flash and blows the
breaker.

What brands have the fuse? I generally buy GE and Philips.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson <thegreatone@example.com> wrote in message news:<4hr49050dvih5khhra0j8ih1m0oeumt915@4ax.com>...
On Thu, 29 Apr 2004 21:26:45 -0700, Kevin McMurtrie
mcmurtri@dslextreme.com> wrote:

about 10 seconds then blew a 20A breaker. Better quality light bulbs
have a fuse wire to prevent this. It's a fire hazard.

Every few months I have a light bulb go with a flash and blows the
breaker.

What brands have the fuse? I generally buy GE and Philips.
Click to expand...

In England they nearly all have a ballotini fuse, its a requirement
here. If it arcs over, the bulb is liable to explode from the sudden
heat applied to the glass. Perhaps arcing over is less of a problem at
110v, I dont know.

A ballotini fuse is easy enough to see: instead of just 2 straight
leads going from filament to base, one lead has a glass capsule
containing a very thin bit of fuse wire part way along - you can
usually see it.

Regards, NT
 
In article <4hr49050dvih5khhra0j8ih1m0oeumt915@4ax.com>,
Jim Thompson <thegreatone@example.com> wrote:

On Thu, 29 Apr 2004 21:26:45 -0700, Kevin McMurtrie
mcmurtri@dslextreme.com> wrote:

In article <a7076635.0404291556.7f06aa77@posting.google.com>,
bigcat@meeow.co.uk (N. Thornton) wrote:

Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?


Regards, NT

The arcing from a break in the filament is really nothing at all. It's
comparable in brightness to shorting a 9V battery.

The spectacular arcs are when the filament shorts the leads, melts the
leads, and then the leads fall on to each other. It draws enough
current to start an electric plasma fire. The best I've seen yet lasted
about 10 seconds then blew a 20A breaker. Better quality light bulbs
have a fuse wire to prevent this. It's a fire hazard.

Every few months I have a light bulb go with a flash and blows the
breaker.

What brands have the fuse? I generally buy GE and Philips.

...Jim Thompson
Click to expand...
You can see the fuse in the clear bulbs. One of the leads near the
socket has a thin section.

The GE clear bulbs have a fuse but their spot halogens don't.
 
"N. Thornton" <bigcat@meeow.co.uk> wrote in message
news:a7076635.0404291556.7f06aa77@posting.google.com...
A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up.
Click to expand...
You sat watching it for 20 minutes, rather than just putting it
out it's misery?
Wassup... getting every last penny's worth out of it, or did you
turn your stereo up and enjoy that disco lights effect?

Seriously, though, they can very often last more than the second you
say. Some can last a while, but I really cannot say that I have stood
watching one to see how long it can suffer for.
Switching it off and back on will end it's torment.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will
destroy a filament in under a second.
Click to expand...
Not always.
Also, it is known that a poor connection can act as a rectifier. This may
lead to some strange effects that may take a while to kill the bulb
completely.

Its a 100w 240v 2000 hour bulb.
Click to expand...
Although they rate bulbs in hours, the life also depends upon how often it
is switched on and off. The surge at switch on does have an effect on the
life of the bulb.
I remember seeing a design for a bulb life extender, where it delayed the
power to the bulb until a low point in the mains cycle. Not sure if it
worked... or if it actually justified the cost when you consider the life of
the added components.

How about a really wild case... a 100 Watt 240v standard mains bulb, used in
an "inspection lamp", exploding with one hell of a bang and glass
everywhere.
Not just one, but replacements doing the same.
The cause was a 100 amp arc welder being used from the same double socket.


LF.
 
In article <a7076635.0404291556.7f06aa77@posting.google.com>, N. Thornton
wrote:
Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?
Click to expand...
I once saw a filament of this arrangement break and form a stable arc in
the gap. I even have a photo of it - although it only came out well
enough to show the bright spots at the broken filament ends being heated
by the arc.
If the electric field (voltage gradient) in the arc exceeds that along
the filament, then the arc will not blow up into a big bright blue flash.
Also, arcs in argon and the usual argon-nitrogen mixture at around
atmospheric pressure to ~1/10 atmosphere with current in the several 10's
of mA to a couple amps are impressively dim, with little radiation output
other than argon's infrared lines and incandescence of whatever the arcs
are connected to.

I have also known linear tubular halogens to form stable burnout arcs.
In those, the gas pressure is higher and the electric field within the arc
is higher.

If the filament breaks while it is hot rather than when it is cold, it
is easier to have a stable burnout arc because the current is lower.
Higher current makes the arc more conductive and easier to blow up into a
big blue flash. Also, a more compact filament design has higher electric
field in the gas and that also makes it easier for the arc to expand and
"blow up".

- Don Klipstein (don@misty.com, http://www.misty.com/~don/index.html)
 
In article <mcmurtri-E493F0.21264529042004@corp-radius.supernews.com>,
Kevin McMurtrie wrote:
In article <a7076635.0404291556.7f06aa77@posting.google.com>,
bigcat@meeow.co.uk (N. Thornton) wrote:

A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

The spectacular arcs are when the filament shorts the leads, melts the
leads, and then the leads fall on to each other.
Click to expand...
Sometimes it works that way, but more often what happens is that the arc
expands until it goes from one filament end to the other, and then not
much is limiting the current through the arc except wiring resistance.
Arcs get more conductive when you push more current through them, to the
point of acting almost like short circuits unless something is limiting
current somewhere.

When a light bulb filament breaks, if the electric field (voltage
gradient) along the filament is greater than that within the arc, then the
arc will expand - usually quite quickly. High current arcs can exist on
cold tungsten - there is such a thing as a "cold cathode arc". That is
usually what is in a xenon flashtube.

When a burnout arc blows up into a big bright blue flash, it is common
(but not guaranteed) to see the filament break in two, sometimes even
three places: Where the original break was, and also at one or both ends
from the arc melting it there once it "blew up" into something drawing a
hundred or so, even more amps.

- Don Klipstein (don@misty.com, http://www.misty.com/~don/index.html)
 
In article <a7076635.0404301544.286c7491@posting.google.com>, N. Thornton
wrote:
Jim Thompson <thegreatone@example.com> wrote in message news:<4hr49050dvih5khhra0j8ih1m0oeumt915@4ax.com>...
On Thu, 29 Apr 2004 21:26:45 -0700, Kevin McMurtrie
mcmurtri@dslextreme.com> wrote:

about 10 seconds then blew a 20A breaker. Better quality light bulbs
have a fuse wire to prevent this. It's a fire hazard.

Every few months I have a light bulb go with a flash and blows the
breaker.

What brands have the fuse? I generally buy GE and Philips.


In England they nearly all have a ballotini fuse, its a requirement
here. If it arcs over, the bulb is liable to explode from the sudden
heat applied to the glass. Perhaps arcing over is less of a problem at
110v, I dont know.

A ballotini fuse is easy enough to see: instead of just 2 straight
leads going from filament to base, one lead has a glass capsule
containing a very thin bit of fuse wire part way along - you can
usually see it.
Click to expand...
120V bulbs usually have the thin piece of fuse wire, but without a glass
capsule.

- Don Klipstein (don@misty.com)
 
In article <409360d4.1@entanet>, L. Fiar wrote:
"N. Thornton" <bigcat@meeow.co.uk> wrote in message
news:a7076635.0404291556.7f06aa77@posting.google.com...

A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up.

You sat watching it for 20 minutes, rather than just putting it
out it's misery?
Wassup... getting every last penny's worth out of it, or did you
turn your stereo up and enjoy that disco lights effect?

Seriously, though, they can very often last more than the second you
say. Some can last a while, but I really cannot say that I have stood
watching one to see how long it can suffer for.
Switching it off and back on will end it's torment.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will
destroy a filament in under a second.

Not always.
Also, it is known that a poor connection can act as a rectifier. This may
lead to some strange effects that may take a while to kill the bulb
completely.

Its a 100w 240v 2000 hour bulb.

Although they rate bulbs in hours, the life also depends upon how often it
is switched on and off. The surge at switch on does have an effect on the
life of the bulb.
Click to expand...
Surprisingly little for most bulbs, actually. What happens is that an
aged filament has a thin spot that suffers a fatal temperature overshoot
during a cold start, and that is why light bulbs so often burn out during
cold starts.
The thin spots that would have a temperature overshoot during a cold
start will not last long if kept running - they tend to deteriorate at a
rate that accelerates worse than exponentially.
More details in a web page of mine:
http://www.misty.com/~don/bulb1.html

I remember seeing a design for a bulb life extender, where it delayed the
power to the bulb until a low point in the mains cycle. Not sure if it
worked... or if it actually justified the cost when you consider the life of
the added components.
Click to expand...
I have seen soft starters with negative temperature coefficient
thermistors. I once did a test to determine the voltage drop of one in
normal use fully warmed up - it dropped enough voltage to explain a 50%
increase in bulb longevity.

- Don Klipstein (don@misty.com)
 
On Sun, 2 May 2004 05:12:06 +0000 (UTC), don@manx.misty.com (Don Klipstein)
wrote:

I once saw a filament of this arrangement break and form a stable arc in
the gap. I even have a photo of it - although it only came out well
enough to show the bright spots at the broken filament ends being heated
by the arc.
Click to expand...
Putting incandescent lamps in a microwave oven is a lot of fun
(even if foolhardy)...

http://amasci.com/weird/microexp.html#bulb
--
-john
wide-open at throttle dot info

~~~~~~~~
"The first step in intelligent tinkering is to
save all the parts." - Aldo Leopold
~~~~~~~~
 
"Don Klipstein" <don@manx.misty.com> wrote in message
news:slrnc991q9.8rr.don@manx.misty.com...
I have seen soft starters with negative temperature coefficient
thermistors. I once did a test to determine the voltage drop of one in
normal use fully warmed up - it dropped enough voltage to explain a 50%
increase in bulb longevity.
Click to expand...
But we are talking pennies for replacement bulbs.
The higher efficiency bulbs are now quite cheap here in the UK, just
a couple of quid or cheaper. Not only do they save in electricity,
but they are claimed to last much longer than a standard bulb.


LF.
 
"L. Fiar" <_@_._> wrote in message news:409b2ead.0@entanet...
"Don Klipstein" <don@manx.misty.com> wrote in message
news:slrnc991q9.8rr.don@manx.misty.com...

I have seen soft starters with negative temperature coefficient
thermistors. I once did a test to determine the voltage drop of one in
normal use fully warmed up - it dropped enough voltage to explain a 50%
increase in bulb longevity.

But we are talking pennies for replacement bulbs.
The higher efficiency bulbs are now quite cheap here in the UK, just
a couple of quid or cheaper. Not only do they save in electricity,
but they are claimed to last much longer than a standard bulb.
Click to expand...
I replaced the 60W incandescent bulb next to the back door of the garage
today with a helically-wound fluorescent. The glass globe over the bulb has
been missing since we bought the house, but i found out that an empty dill
pickle jar fits perfectly.
 
"Don Klipstein" <don@manx.misty.com> wrote in message
news:slrnc991q9.8rr.don@manx.misty.com...
More details in a web page of mine:
http://www.misty.com/~don/bulb1.html
Click to expand...
Very illuminating, it certainly threw some light on the subject.
I am no longer in the dark about it.

I do hate when sites use Flash, Active-X and scripting where it is not
needed, so your site is a rather refreshing change.

OK to link from my site?
 
"L. Fiar" <_@_._> wrote in message news:409e6c02.0@entanet...
"Don Klipstein" <don@manx.misty.com> wrote in message
news:slrnc991q9.8rr.don@manx.misty.com...

More details in a web page of mine:
http://www.misty.com/~don/bulb1.html

Very illuminating, it certainly threw some light on the subject.
I am no longer in the dark about it.

I do hate when sites use Flash, Active-X and scripting where it is not
needed, so your site is a rather refreshing change.

OK to link from my site?

Nice site. Do you write HOWTOS as well? :)
Click to expand...

Cheers!
Rich
 
in article a7076635.0404291556.7f06aa77@posting.google.com, N. Thornton at
bigcat@meeow.co.uk wrote on 4/29/04 18:56:

Hi


A light bulb went today - but its way of going out is a complete
puzzle. I know they can act up for a second or less, but this one was
doing all sorts of weird things for a good 20 minutes before it
finally gave up. Much of the time it was flashing at maybe 8 or 10Hz,
most of the time its output was well below normal. At times it pulsed
at praps 2 or 3 Hz, sometimes went very very dim for a few seconds
then brightened up again.

It cant be down to filament evaporation surely.
It surely cant be down to arcing either, as arcs will destroy a
filament in under a second.
And I dont see how it would be a loose connection: the behaviour was
far too regular, and the filament survived far too long.
What on earth was going on?

I got a bit of a look at the element, its arranged as a 3/4 circle,
and all looked intact except the end 2 sections. Its a 100w 240v 2000
hour bulb.

Anyone know how it could do all this? Should I be asking News2020?


Regards, NT
Click to expand...
I have seen dozens of examples of 60-100 watt severe-service bulbs used in
'drop light' portable work light fixtures fall to the floor and suddenly get
much brighter for 5-30 minutes, then 'flash' out. I assume they are either
arcing, oxygen getting in and burning the filiment, or the filiment shorts
(literally) to itself. New bulbs won't do this; only ones used for several
hours. I guess I ought to do a postmortem on one to be sure.
HTH
Dave Cole
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top