It really could be either... normally you would suspect the CCFL
backlight (Cold Cathode Flourescent Lamp), they'er about the
thickness of a thin knitting needle, the length depending on size of
the screen.

The lamps would tend to show some signs such as the Whites in the
display turning to a tinted colour or sometimes the tubes produce a
flicker... but these inverters that produce about 1.8KV contains
surface mounted devices which can sometimes fail.

The tubes when on their way out 'may' show some blackning at the ends
which 'may' provide a clue.

The tubes contain an electrode at both ends and filled with gas that
is ionised to produce the light, there is no heaters at the ends of
the tubes like there are in ones you see in standard flourescent
lamps.

Davy

"Davy" <no@spam.invalid> wrote in message
news:12n9893m3mab12b@news.supernews.com...
>
> The tubes contain an electrode at both ends and filled with gas that
> is ionised to produce the light, there is no heaters at the ends of
> the tubes like there are in ones you see in standard flourescent
> lamps.
>
Not necessarily the case. Many so called Cold Cathode tubes do in fact have
a heater at both ends of the tube. The description is a nominal one as the
electrodes of heaterless tubes get just as hot as heated ones when in use.

M.I.5? wrote:

> Not necessarily the case. Many so called Cold Cathode tubes do in fact have
> a heater at both ends of the tube. The description is a nominal one as the

Never seen one. It's easy to verify this, anyway - a CCFL will have
only one, high-dielectric-insulated wire going to each end. If it has
more than one wire, then (a) it's a heated tube, and (b) it's by
definition not a CCFL.

I have never seen a heated fluorescent in an LCD application. I don't
believe they are ever used this way.

M.I.5? wrote:
> "Davy" <no@spam.invalid> wrote in message
> news:12n9893m3mab12b@news.supernews.com...
>>
>> The tubes contain an electrode at both ends and filled with gas that
>> is ionised to produce the light, there is no heaters at the ends of
>> the tubes like there are in ones you see in standard flourescent
>> lamps.
>>
> Not necessarily the case. Many so called Cold Cathode tubes do in
> fact have a heater at both ends of the tube.

Then they're not CCFLs, by definition.

I've never seen an LCD backlight that would match your description, got an
example?
--
James

Visit the Thinkpad Forums
http://forum.thinkpads.com

The second part of your comment may be true, but I've NEVER seen lamp in
an LCD display that had heaters like lighting fluorescent lamps do.
There is one wire coming out of each end, period. No heater. The term
"CCFT" means no heater, and in that sense it's not used "nominally",
although the ends might get hot while the lamp is running.

M.I.5? wrote:
> "Davy" <no@spam.invalid> wrote in message
> news:12n9893m3mab12b@news.supernews.com...
>> The tubes contain an electrode at both ends and filled with gas that
>> is ionised to produce the light, there is no heaters at the ends of
>> the tubes like there are in ones you see in standard flourescent
>> lamps.
>>
> Not necessarily the case. Many so called Cold Cathode tubes do in fact have
> a heater at both ends of the tube. The description is a nominal one as the
> electrodes of heaterless tubes get just as hot as heated ones when in use.
>
>

"Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
news:45758bdc$0$13742$4c368faf@roadrunner.com
> M.I.5? wrote:
>> "Davy" <no@spam.invalid> wrote in message
>> news:12n9893m3mab12b@news.supernews.com...
>>> The tubes contain an electrode at both ends and filled with gas that
>>> is ionised to produce the light, there is no heaters at the ends of
>>> the tubes like there are in ones you see in standard flourescent
>>> lamps.
>>>
>> Not necessarily the case. Many so called Cold Cathode tubes do in
>> fact have a heater at both ends of the tube. The description is a
>> nominal one as the electrodes of heaterless tubes get just as hot as
>> heated ones when in use.
>
> The second part of your comment may be true, but I've NEVER seen lamp
> in an LCD display that had heaters like lighting fluorescent lamps do.
> There is one wire coming out of each end, period. No heater. The
> term "CCFT" means no heater, and in that sense it's not used
> "nominally", although the ends might get hot while the lamp is
> running.

Cold cathode works the same way, minus the heater. How cold cathode
works without the heater is to increase the voltage about 50% higher to
get it started. Even the heated kind only needs the heater when it first
starts. So you need to heat the cathode or increase the voltage until it
starts. Otherwise there is no difference in operation.

Although M.I.5¾ seems to feel that cold cathode runs hot. Although I
feel it isn't do to the cold cathode design, but the small size which
causes all of the heat. As technically, once it starts to ionize (within
a second most of the time), both types works the same.

--
Bill

<zwsdotcom******.com> wrote in message
news:1165320901.492423.82610@f1g2000cwa.googlegrou ps.com...
>
> M.I.5? wrote:
>
>> Not necessarily the case. Many so called Cold Cathode tubes do in fact
>> have
>> a heater at both ends of the tube. The description is a nominal one as
>> the
>
> Never seen one. It's easy to verify this, anyway - a CCFL will have
> only one, high-dielectric-insulated wire going to each end. If it has
> more than one wire, then (a) it's a heated tube, and (b) it's by
> definition not a CCFL.
>

Agreed, but they still get sold as Cold Cathode Tubes. It seems to be the
small size that determines the description.

> I have never seen a heated fluorescent in an LCD application. I don't
> believe they are ever used this way.
>

I have, but not in any LCD display produced in the last 3 years, and
admitedly not in any laptop display. They used to be quite common in
specialised displays.

M.I.5¾ wrote:

> > I have never seen a heated fluorescent in an LCD application. I don't
> > believe they are ever used this way.
>
> I have, but not in any LCD display produced in the last 3 years, and
> admitedly not in any laptop display. They used to be quite common in
> specialised displays.

Specialized how? Extended temperature aerospace/automotive panels?

<zwsdotcom******.com> wrote in message
news:1165415104.648479.52180@79g2000cws.googlegrou ps.com...

M.I.5¾ wrote:

> > I have never seen a heated fluorescent in an LCD application. I don't
> > believe they are ever used this way.
>
> I have, but not in any LCD display produced in the last 3 years, and
> admitedly not in any laptop display. They used to be quite common in
> specialised displays.

Specialized how? Extended temperature aerospace/automotive panels?

-----------------------

More like specialised test equipment.

"JHEM" <James@ESAD.SPAMMERS.thinkpads.com> wrote in message
news:b7fdh.2066$5D1.1634@trnddc06...
> M.I.5? wrote:
>> "Davy" <no@spam.invalid> wrote in message
>> news:12n9893m3mab12b@news.supernews.com...
>>>
>>> The tubes contain an electrode at both ends and filled with gas that
>>> is ionised to produce the light, there is no heaters at the ends of
>>> the tubes like there are in ones you see in standard flourescent
>>> lamps.
>>>
>> Not necessarily the case. Many so called Cold Cathode tubes do in
>> fact have a heater at both ends of the tube.
>
> Then they're not CCFLs, by definition.
>

Tell the manufacturers, not me. I quite agree.

> I've never seen an LCD backlight that would match your description, got an
> example?
> --
> James
>
> Visit the Thinkpad Forums
> http://forum.thinkpads.com
>

"BillW50" <BillW50@aol.kom> wrote in message
news:4576039b$0$1347$834e42db@reader.greatnowhere. com...
> "Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
> news:45758bdc$0$13742$4c368faf@roadrunner.com
>> M.I.5? wrote:
>>> "Davy" <no@spam.invalid> wrote in message
>>> news:12n9893m3mab12b@news.supernews.com...
>>>> The tubes contain an electrode at both ends and filled with gas that
>>>> is ionised to produce the light, there is no heaters at the ends of
>>>> the tubes like there are in ones you see in standard flourescent
>>>> lamps.
>>>>
>>> Not necessarily the case. Many so called Cold Cathode tubes do in
>>> fact have a heater at both ends of the tube. The description is a
>>> nominal one as the electrodes of heaterless tubes get just as hot as
>>> heated ones when in use.
>>
>> The second part of your comment may be true, but I've NEVER seen lamp
>> in an LCD display that had heaters like lighting fluorescent lamps do.
>> There is one wire coming out of each end, period. No heater. The
>> term "CCFT" means no heater, and in that sense it's not used
>> "nominally", although the ends might get hot while the lamp is
>> running.
>
> Cold cathode works the same way, minus the heater. How cold cathode works
> without the heater is to increase the voltage about 50% higher to get it
> started. Even the heated kind only needs the heater when it first starts.
> So you need to heat the cathode or increase the voltage until it starts.
> Otherwise there is no difference in operation.
>

Agreed. But it is the manufacturers who have chosen to describe them as
cold cathode not me.

> Although M.I.5¾ seems to feel that cold cathode runs hot. Although I feel
> it isn't do to the cold cathode design, but the small size which causes
> all of the heat. As technically, once it starts to ionize (within a second
> most of the time), both types works the same.
>

The outside of a Cold Cathode tube may remain cool, but the electrodes
inside the tube operate at near red heat once the tube has warmed up - a
process that takes a minute or two. The tube current generally falls as the
brightness increases (due to the increasing gas pressure). The actual light
generated by the discharge actually falls as well, but the wavelength
shortens and moves into the operating band of the phosphor, hence the
increase in white light output.

"JHEM" <James@ESAD.SPAMMERS.thinkpads.com> wrote in message
news:b7fdh.2066$5D1.1634@trnddc06...
> M.I.5? wrote:
>> "Davy" <no@spam.invalid> wrote in message
>> news:12n9893m3mab12b@news.supernews.com...
>>>
>>> The tubes contain an electrode at both ends and filled with gas that
>>> is ionised to produce the light, there is no heaters at the ends of
>>> the tubes like there are in ones you see in standard flourescent
>>> lamps.
>>>
>> Not necessarily the case. Many so called Cold Cathode tubes do in
>> fact have a heater at both ends of the tube.
>
> Then they're not CCFLs, by definition.
>
> I've never seen an LCD backlight that would match your description, got an
> example?

I was hoping to post a link to one of the many suppliers, but I note from my
current crop of catalogues that replacement CCFL lamps have all but
disappeared from them. Virtually every catalogue now has a token single
lamp. A year ago, they had every size imaginable.

Now I've got a problem next time a backlight goes.

M.I.5¾ wrote:

> > admitedly not in any laptop display. They used to be quite common in
> > specialised displays.
>
> Specialized how? Extended temperature aerospace/automotive panels?
>
> More like specialised test equipment.

You intrigued me here, so I opened my TDS210 (CCFL-backlit STN LCD
oscilloscope) and no it's really a CCFL. What kind of test equipment do
you have in mind?

<zwsdotcom******.com> wrote in message
news:1165486993.481153.264430@16g2000cwy.googlegro ups.com...

M.I.5¾ wrote:

> > admitedly not in any laptop display. They used to be quite common in
> > specialised displays.
>
> Specialized how? Extended temperature aerospace/automotive panels?
>
> More like specialised test equipment.

You intrigued me here, so I opened my TDS210 (CCFL-backlit STN LCD
oscilloscope) and no it's really a CCFL. What kind of test equipment do
you have in mind?

--------------------------------

Bespoke test equipment used in the aerospace industry. In many cases, they
are either unique or there are only 3 or 4 in existence.

M.I.5¾ wrote:

> I was hoping to post a link to one of the many suppliers, but I note from my
> current crop of catalogues that replacement CCFL lamps have all but
> disappeared from them. Virtually every catalogue now has a token single
> lamp. A year ago, they had every size imaginable.

Digikey lists five different ones in their catalogue ranging from 2.2 -
3.1 mm dia and 100 - 418 mm long with leads attached.

Ian Singer

--


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