Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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What is the purpose of the small neon bulb by the flyback on older TVs? (I haven't noticed it in any modern tvs.)
Someone asked me that the other day and I couldn't answer! Seems like I used to know (I'm an old-timer) but can't remember.
Thanks.
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"oldfogie" wrote in message
.. .
What is the purpose of the small neon bulb by the flyback on older TVs? (I
haven't noticed it in any modern tvs.)

A voltage clipper? Neon lamps have very high resistance and then drop to a
low resistance when the gas ionizes. About 60 volts, I think.


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oldfogie wrote:
What is the purpose of the small neon bulb by the flyback on older TVs? (I haven't noticed it in any modern tvs.)
Someone asked me that the other day and I couldn't answer! Seems like I used to know (I'm an old-timer) but can't remember.
Thanks.

50-100 volt spike clamp??
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oldfogie wrote:

What is the purpose of the small neon bulb by the flyback on older TVs? (I haven't noticed it in any modern tvs.)
Someone asked me that the other day and I couldn't answer! Seems like I used to know (I'm an old-timer) but can't remember.
Thanks.


Could be a voltage reference (~60 - 90 V), voltage drop or translation,
a hysteresis element in a multivibrator, clamp or even indicator of
some circuit's status.

Regards,

Michael
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Are you sure it is really a neon bulb? I'm thinking it is possibly a high
voltage spark gap which serves as overvoltage protection... Just my
thoughts. Without seeing it it would be hard to say for sure.

Bob

"oldfogie" wrote in message
.. .
What is the purpose of the small neon bulb by the flyback on older TVs? (I
haven't noticed it in any modern tvs.)
Someone asked me that the other day and I couldn't answer! Seems like I used
to know (I'm an old-timer) but can't remember.
Thanks.




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On Jan 28, 6:28�pm, "Bob Shuman" wrote:
Are you sure it is really a neon bulb? � I'm thinking it is possibly a high
voltage spark gap which serves as overvoltage protection... �Just my
thoughts. �Without seeing it it would be hard to say for sure.

� � Bob

"oldfogie" wrote in message

.. .
What is the purpose of the small neon bulb by the flyback on older TVs? (I
haven't noticed it in any modern tvs.)
Someone asked me that the other day and I couldn't answer! Seems like I used
to know (I'm an old-timer) but can't remember.
Thanks.


I'll bet it's a solid state GE from the early 1970s. They included the
bulb as a high-voltage indicator. This was to deter arcing with a
screwdriver as a test.
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Yes, I'm sure, was a small glass neon bulb soldered to chassis.
I looked through a good many old Sams folders, back into the '70s & '80s but never found a neon bulb in one. Problem is, just because it was near the fly doesn't have to mean it was in the fly circuit. So it must have been in some other circuit. I think it was for spike protection, for whatever circuit it was in.
I'm ready to just forget it, not important.
Thanks to all for replies!


"Bob Shuman" wrote in message ...
Are you sure it is really a neon bulb? I'm thinking it is possibly a high
voltage spark gap which serves as overvoltage protection... Just my
thoughts. Without seeing it it would be hard to say for sure.

Bob

"oldfogie" wrote in message
.. .
What is the purpose of the small neon bulb by the flyback on older TVs? (I
haven't noticed it in any modern tvs.)
Someone asked me that the other day and I couldn't answer! Seems like I used
to know (I'm an old-timer) but can't remember.
Thanks.


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A real neon bulb? I wish I owned a million of them, I love neon
lights/neon signs.I own an old broken neon NO VACANCY sign I bought at
the Goodwill store years ago.It was broken when I bought it.I like it
anyway.I think it dates back to the 1940s or 1950s.Nothing beats neon
lights and neon signs.
cuhulin

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I think it was used as a high-voltage clipper... sort of a high-voltage
zener diode. During normal operation it's never supposed to light up. I
often saw those on neck boards of old monochrome video monitors. Only once
did I ever see one light up and that was due to picture tube failure (the
precise details of which I can't remember now). The firing voltage of neon
bulbs is pretty high... at least 50 volts, some go as high as 90 volts.

BTW: If the bulb is placed across DC, only one of the interior electrodes
will light up. If the bulb is placed across AC, then both internal
electrodes will light up.




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"oldfogie" wrote in message
...
Yes, I'm sure, was a small glass neon bulb soldered to chassis.
I looked through a good many old Sams folders, back into the '70s & '80s
but never found a neon bulb in one. Problem is, just because it was near
the fly doesn't have to mean it was in the fly circuit. So it must have
been in some other circuit. I think it was for spike protection, for
whatever circuit it was in.
I'm ready to just forget it, not important.
Thanks to all for replies!




If it was a true neon bulb, then it wouldn't actually need to be connected
into any circuitry in order to light up as an indicator of flyback activity.
Most gas filled tubes will light in mid air if they are in close enough
proximity to a flyback tranny. Back when I was an apprentice, like 35 years
ago, the guy that I worked under in a TV workshop, used to keep a short thin
flourescent tube on his bench. He used this to test for horizontal output
stage activity, simply by waving it around the FB tranny. As I recall, he
used to reckon that he could tell a lot about how that stage was working,
when he had a lack of picture fault, just by the 'way' in which his little
tube lit up.

Most of the similar 'bulbs' that I've seen on CRT base connector boards,
have been gas-filled spark gaps. I seem to recall that they used to put
argon in them, and when they went off as a result of an inter-electrode
short in the tube, they lit up white, rather than the orange glow of a neon.

Arfa





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On Tue, 29 Jan 2008 13:46:44 GMT, "Arfa Daily"
wrote:



If it was a true neon bulb, then it wouldn't actually need to be connected
into any circuitry in order to light up as an indicator of flyback activity.
Most gas filled tubes will light in mid air if they are in close enough
proximity to a flyback tranny. Back when I was an apprentice, like 35 years
ago, the guy that I worked under in a TV workshop, used to keep a short thin
flourescent tube on his bench. He used this to test for horizontal output
stage activity, simply by waving it around the FB tranny. As I recall, he
used to reckon that he could tell a lot about how that stage was working,
when he had a lack of picture fault, just by the 'way' in which his little
tube lit up.


Years ago, we'd just tape or glue a neon bulb on either a dowel or a
pencil. Then someone realized that pencil lead conducts and the dowel
method became much more popular!
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Assuming the HV supply is still good, you should have it rebuilt. Neon
signmakers are plentiful, generally do good worrk, and can duplicate any
tube you bring them.

Just a thought.



Even if it weren't, used neon transformers are cheap.

I haven't heard anything but incoherent rantings from that guy though, I
dunno what he's doing on this group. Nothing he posts makes any sense, or
has anything to do with electronics repair.


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wrote in message ...

Which reminds me. I have an old neon bulb nightlight. This thing
is confused and retarded. If the room is dark, it does not light. But
when I flip on the ceiling lights in the room, or point a flashlight
at it, the neon lights up...
I think it's just plain old, but I leave it there just because it's a
conversation piece.


Believe it or not, this is more or less normal for an old neon bulb.

Ambient light knocks electrons off the neon atoms in the bulb, _lowering_
the threshold voltage. This bulb has aged to the point where the line
voltage isn't high enough to light it _until_ room light or a flashlight
"kicks butt" on them-there outer-orbital 'lectrons.


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My old NO VACANCY neon sign is an old metal box, the old brown paint on
the box is very faded.The neon glass tubes, some parts of the glass
tubes are completly broken away, missing.The box still has the old high
voltage power thingy in it.I don't think there is anybody in my local
city area who builds/repairs old neon signs.I only hang onto it because
it is very old and I like to collect all kinds of very old things.The
Postman Always Rings Twice old movie.That poor cat got zapped on that
neon sign.
cuhulin



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someguy@ invalid.com wrote:
I have an old neon bulb nightlight. This thing is confused and retarded.
If the room is dark, it does not light.
But when I flip on the ceiling lights in the room,
or point a flashlight at it, the neon lights up...
I think it's just plain old,

William Sommerwerck wrote
WITHOUT ATTRIBUTION TO THE PREVIOUS POSTER:
Believe it or not, this is more or less normal for an old neon bulb.

Yup.
In the '60s, electronic organs used neons in their percussion circuits
(e.g. a Xylophone tab).
Incandescents were positioned inside the unit near the neons
so that NE-2s were "biased".
When someone said his precussion stopped working,
you made sure your stock of mini incandescents was up to snuff.
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Arfa Daily wrote:
Back when I was an apprentice, like 35 years ago,
the guy that I worked under in a TV workshop,
used to keep a short thin flourescent tube on his bench.
He used this to test for horizontal output stage activity,
simply by waving it around the FB tranny[...]

Old tricks are so cool.

Most of the similar 'bulbs' that I've seen on CRT base connector boards,
have been gas-filled spark gaps. I seem to recall that they used to put
argon in them, and when they went off as a result of an inter-electrode
short in the tube, they lit up white, rather than the orange glow of a neon.

Well, Argon would be the cheapest
--but the Argon stuff I've seen glows purple.
Maybe those are a different gas--or a gas mixture.
http://www.google.com/search?q=cache...righter.orange
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"James Sweet" wrote in message
news:%8Nnj.3854$1f.2860@trndny02...

"Tim" wrote in message
...
In article ,
says...
My old NO VACANCY neon sign is an old metal box, the old brown paint on
the box is very faded.The neon glass tubes, some parts of the glass
tubes are completly broken away, missing.The box still has the old high
voltage power thingy in it.I don't think there is anybody in my local
city area who builds/repairs old neon signs.I only hang onto it because
it is very old and I like to collect all kinds of very old things.The
Postman Always Rings Twice old movie.That poor cat got zapped on that
neon sign.
cuhulin


You could always use those Cold Cathode light ropes they sell for
computer case modding. They could bring the neon look back to life, with
no HV problems to deal with.

- Tim -


Or just send the glass out to have it fixed properly. I dunno how it's
possible to live to far from a neon shop, there's lots of mom & pop joints
still spread around the country. The craft nearly died out for a while,
but in the last couple decades there's been somewhat of a revival. Once
have the sign box with the transformer, it's not terribly expensive to
have new units made for a simple sign like that.

There's LED "neon" out these days, but nothing comes close to the real
thing, it just doesn't look right.


Yup ! 'Neon' tubework has a look all of its own. When I first went to Vegas
probably 20 odd years ago, it was all neon. Now, with a few exceptions like
the main signage at Flamingo, and one or two machine banks on the casino
floor, the Strip is now predominantly lit by LEDs and LED giant screen TVs.
There's still some original-style neon tubework downtown at the Golden
Nugget and so on, but not a lot any more. The neon had a much more 'organic'
feel about it, I think. Kinda like the difference between film and video.
Still very pretty there, and unlike anywhere else on earth, but not quite as
'warm' feeling as in the old days ...

Arfa




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"JeffM" wrote in message
...
Arfa Daily wrote:
Back when I was an apprentice, like 35 years ago,
the guy that I worked under in a TV workshop,
used to keep a short thin flourescent tube on his bench.
He used this to test for horizontal output stage activity,
simply by waving it around the FB tranny[...]

Old tricks are so cool.

Most of the similar 'bulbs' that I've seen on CRT base connector boards,
have been gas-filled spark gaps. I seem to recall that they used to put
argon in them, and when they went off as a result of an inter-electrode
short in the tube, they lit up white, rather than the orange glow of a
neon.

Well, Argon would be the cheapest
--but the Argon stuff I've seen glows purple.
Maybe those are a different gas--or a gas mixture.


You could very well be right - it's been a long time since I was
commercially involved in TV repair and doing it all day every day. I'm
pretty sure that they were argon filled, and I had this recollection of the
discharge being white or blue/white, but the old memory is not what it was
any more. Hell, I have trouble remembering what I had for breakfast these
days - well, not quite, but you know what I mean !

Arfa


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On Jan 28, 5:56*pm, "Charles" wrote:
"oldfogie" wrote in message

.. .
What is the purpose of the small neon bulb by the flyback on older TVs? (I
haven't noticed it in any modern tvs.)

A voltage clipper? *Neon lamps have very high resistance and then drop to a
low resistance when the gas ionizes. *About 60 volts, I think.


Zenith liked to use them on their mid 60's - early 70's tube sets.
They seemed to use them for several purposes in the horiz. sweep
circuit.
I remember some 16" - 19" B&W portables where the neon bulb lit up
constantly
when the set was on. I have a 25CC50 chassis color set that uses two
in series in the HV regulator circuit. They light for a few seconds
after the
horiz. sweep starts then go out once the HV comes up.

Mike
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James Sweet wrote:


Assuming the HV supply is still good, you should have it rebuilt. Neon
signmakers are plentiful, generally do good worrk, and can duplicate any
tube you bring them.

Just a thought.


Even if it weren't, used neon transformers are cheap.

I haven't heard anything but incoherent rantings from that guy though, I
dunno what he's doing on this group. Nothing he posts makes any sense, or
has anything to do with electronics repair.



He trolls a lot of groups. Take a look at his rantings on
news:rec.radio.shortwave if you need proof.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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Michael A. Terrell wrote:
James Sweet wrote:
Assuming the HV supply is still good, you should have it rebuilt. Neon
signmakers are plentiful, generally do good worrk, and can duplicate any
tube you bring them.

Just a thought.

Even if it weren't, used neon transformers are cheap.

I haven't heard anything but incoherent rantings from that guy though, I
dunno what he's doing on this group. Nothing he posts makes any sense, or
has anything to do with electronics repair.



He trolls a lot of groups. Take a look at his rantings on
news:rec.radio.shortwave if you need proof.

I think he's fairly innocuous; but it does appear that he's often
well-lubricated when he pushes the 'send' button. Basically, I think
he's just lonely...but annoying at times.

jak
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jakdedert wrote:

I think he's fairly innocuous; but it does appear that he's often
well-lubricated when he pushes the 'send' button. Basically, I think
he's just lonely...but annoying at times.



If he's lonely, he needs to find someplace to do volunteer work. Find
a place where he can interact with others, rather than spend his time
bothering people online. Life is too short alredy, so live it while you
can.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida


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"Michael A. Terrell" wrote in message
...
jakdedert wrote:


I think he's fairly innocuous; but it does appear that he's often
well-lubricated when he pushes the 'send' button. Basically,
I think he's just lonely...but annoying at times.


If he's lonely, he needs to find someplace to do volunteer work.
Find a place where he can interact with others, rather than
spend his time bothering people online.


I wish him luck finding it. In the Fall of 2004 I was unemployed and looking
for a way to usefully spend my time (if only to lighten my depression). When
I applied to the King County Library System to tutor kids in math and
science, I was immediately rejected as "unqualified".

Hell, I was accepted by Caltech, MIT, and Case.

I haven't looked for volunteer work since.


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William Sommerwerck wrote:

"Michael A. Terrell" wrote in message
...
jakdedert wrote:


I think he's fairly innocuous; but it does appear that he's often
well-lubricated when he pushes the 'send' button. Basically,
I think he's just lonely...but annoying at times.


If he's lonely, he needs to find someplace to do volunteer work.
Find a place where he can interact with others, rather than
spend his time bothering people online.


I wish him luck finding it. In the Fall of 2004 I was unemployed and looking
for a way to usefully spend my time (if only to lighten my depression). When
I applied to the King County Library System to tutor kids in math and
science, I was immediately rejected as "unqualified".



Some only accept retired teachers, for some reason.


Hell, I was accepted by Caltech, MIT, and Case.

I haven't looked for volunteer work since.



There are a lot of retirement homes around here that welcome people
to spend time with the residents. Non profit thrift stores and various
clubs always need help. A friend has had to depend on community service
workers lately for his thrift store. The Humane Society, Habitat for
Humanity and any VA clinic or hospital needs volunteers. The local VA
clinics are all desperate for volunteer drivers, to drive the eight
passenger DAV vans from local clinics to the Gainsville VA hospital.
The local United Way has a list of about 100 organizations needing help.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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"Michael A. Terrell"
wrote in message ...

There are a lot of retirement homes around here that welcome
people to spend time with the residents.


There's a hospital not far from me, and I've considered going in. The
problem is that I'm not quite yet ready to listen to people talk on
ad-infinitum.

I appreciate your suggestions, though, and will keep them in mind. At the
moment, my car is not running reliably.


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