Hi All,

I have a pre-lit, 12', 5-year old Christmas tree with about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's not
a broken wire.

The first bulb in each section is a non-removable, non-shunt type bulb. The
directions say only that it is a safety bulb and cannot be replaced. On at
least one string, this safety bulb appears to be blown.

What gives here? I have shunt bulbs that are supposed to keep a blown bulb
from taking out the whole section, but yet they are all out. I have line
voltage all the way through the string, and yet no lights. And I have a
"safety bulb" that cannot be replaced, yet is blown.

What happens if I cut the safety bulb off (it's molded into its socket) and
twist the three wires together. What safety can this be providing any way?
Any other ideas, aside from what we did last year - just throw a set of
lights on it, which defeats the purpose of paying the price for a pre-lit
tree?

This is driving me and my wife insane.

Thanks in advance for your input.

Reactor wrote:

Hi All,

I have a pre-lit, 12', 5-year old Christmas tree with about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's not
a broken wire.

The first bulb in each section is a non-removable, non-shunt type bulb. The
directions say only that it is a safety bulb and cannot be replaced. On at
least one string, this safety bulb appears to be blown.

What gives here? I have shunt bulbs that are supposed to keep a blown bulb
from taking out the whole section, but yet they are all out. I have line
voltage all the way through the string, and yet no lights. And I have a
"safety bulb" that cannot be replaced, yet is blown.

What happens if I cut the safety bulb off (it's molded into its socket) and
twist the three wires together. What safety can this be providing any way?
Any other ideas, aside from what we did last year - just throw a set of
lights on it, which defeats the purpose of paying the price for a pre-lit
tree?

This is driving me and my wife insane.

Thanks in advance for your input.


The fact that are getting voltage at the end of the string does not
mean alot to me. You didn't indicate what method you used to determine
this? Did you use a field won maybe? if so, That most likely will yield
incorrect results..
The Safety lamp might be in series with the return path..
First try a small 120 Volt incandescent lamp in place of the safety
lamp.
The whole idea is to have that lamp absorb the whole load in the
case where the string may become shorted.

that is just an idea.. May not be fact but I wouldn't use anything
other than another bulb to test the string.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

"Reactor" bruce.gettel-at-myactv.net wrote in message
...
Hi All,

I have a pre-lit, 12', 5-year old Christmas tree with about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's
not a broken wire.

The first bulb in each section is a non-removable, non-shunt type bulb.
The directions say only that it is a safety bulb and cannot be replaced.
On at least one string, this safety bulb appears to be blown.

What gives here? I have shunt bulbs that are supposed to keep a blown
bulb from taking out the whole section, but yet they are all out. I have
line voltage all the way through the string, and yet no lights. And I
have a "safety bulb" that cannot be replaced, yet is blown.

What happens if I cut the safety bulb off (it's molded into its socket)
and twist the three wires together. What safety can this be providing any
way? Any other ideas, aside from what we did last year - just throw a set
of lights on it, which defeats the purpose of paying the price for a
pre-lit tree?

This is driving me and my wife insane.

Thanks in advance for your input.


I've never seen a set with a "safety bulb", but apparently it serves as a
fuse? Personally I would bypass it and instead put an inline fuse in the
set, but I don't recommend others to bypass safety features, use common
sense with this.

For the other bulbs, I've seen a lot of problems with bad connections in the
sockets or broken wire leads on the bulbs cause sets to be out. It can be
frustrating, but a multimeter works well to track down the open.

On Nov 17, 10:01 pm, Jamie
t wrote:
Reactor wrote:
Hi All,

I have a pre-lit, 12', 5-year old Christmas tree with about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's not
a broken wire.

The first bulb in each section is a non-removable, non-shunt type bulb. The
directions say only that it is a safety bulb and cannot be replaced. On at
least one string, this safety bulb appears to be blown.

What gives here? I have shunt bulbs that are supposed to keep a blown bulb
from taking out the whole section, but yet they are all out. I have line
voltage all the way through the string, and yet no lights. And I have a
"safety bulb" that cannot be replaced, yet is blown.

What happens if I cut the safety bulb off (it's molded into its socket) and
twist the three wires together. What safety can this be providing any way?
Any other ideas, aside from what we did last year - just throw a set of
lights on it, which defeats the purpose of paying the price for a pre-lit
tree?

This is driving me and my wife insane.

Thanks in advance for your input.

The fact that are getting voltage at the end of the string does not
mean alot to me. You didn't indicate what method you used to determine
this? Did you use a field won maybe? if so, That most likely will yield
incorrect results..
The Safety lamp might be in series with the return path..
First try a small 120 Volt incandescent lamp in place of the safety
lamp.
The whole idea is to have that lamp absorb the whole load in the
case where the string may become shorted.

that is just an idea.. May not be fact but I wouldn't use anything
other than another bulb to test the string.

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.http://webpages.charter.net/jamie_5- Hide quoted text -

- Show quoted text -

Hi,

I used a Fluke multimeter, plugged into the female socket at the end
of the string. Good voltage and it doesn't change when I move the
string of lights around, so I think the string is solid.

I can't replace the "safety bulb" with anything without cutting into
the string. These are the very small incandescent lamps with the tiny
wire leads.

On Nov 17, 9:10 pm, "Reactor" bruce.gettel-at-myactv.net wrote:
Hi All,

I have a pre-lit, 12', 5-year old Christmas tree with about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's not
a broken wire.

The first bulb in each section is a non-removable, non-shunt type bulb. The
directions say only that it is a safety bulb and cannot be replaced. On at
least one string, this safety bulb appears to be blown.

What gives here? I have shunt bulbs that are supposed to keep a blown bulb
from taking out the whole section, but yet they are all out. I have line
voltage all the way through the string, and yet no lights. And I have a
"safety bulb" that cannot be replaced, yet is blown.

What happens if I cut the safety bulb off (it's molded into its socket) and
twist the three wires together. What safety can this be providing any way?
Any other ideas, aside from what we did last year - just throw a set of
lights on it, which defeats the purpose of paying the price for a pre-lit
tree?

This is driving me and my wife insane.

Thanks in advance for your input.

Here's an update.

In tracking down and replacing numerous burnt lamps, The back half -
the side closest to the far end of the string - suddenly lit up.

What is strange is that I was working on the end closest to the plug
at the time.

Also, I have replaced all burnt bulbs with new ones that were tested
prior to installation. Now I have half a string that does not light
for no obvious reason.

Keep the thoughts coming . . . I'll keep playing with this as long as
my sanity holds out . . . ..

Thanks.

"Reactor" bruce.gettel-at-myactv.net hath wroth:

I have a pre-lit, 12', 5-year old Christmas tree with about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's not
a broken wire.

It's not quite what you think. See explanation at:
http://www.planetchristmas.com/Minis.htm
http://christmas.howstuffworks.com/christmas-lights2.htm

The first bulb in each section is a non-removable, non-shunt type bulb. The
directions say only that it is a safety bulb and cannot be replaced. On at
least one string, this safety bulb appears to be blown.

The first bulb is a little different from the others. It does NOT
contain an automatic shunting crowbar or shunt resistor inside. If it
blows, the whole string goes off. That's because it's connected
directly to the 117VAC power mains. If the bulb were removed, and
some kid shoved a paper clip into the socket, they might get the full
force of the 117VAC power. If they did that with any other lamp in
the circuit, the safety lamp would limit current and possibly act as a
fuse.

What gives here? I have shunt bulbs that are supposed to keep a blown bulb
from taking out the whole section, but yet they are all out. I have line
voltage all the way through the string, and yet no lights. And I have a
"safety bulb" that cannot be replaced, yet is blown.

If all the shunts in the string decided to close after the bulb
filament blew, then it's highly likely that the safety bulb would also
blow. My guess(tm) is that the only way for that to happen is
overheating or excessive inrush current. Do the other lights get
unusually hot or seem unusually bright? Is there proper air flow? Do
you have it near a fireplace or heater?

What happens if I cut the safety bulb off (it's molded into its socket) and
twist the three wires together.

Poof. The 3rd wire goes to the connector at the end of the string, so
that the next block of lights can be powered. In effect, it forms an
extension cord for the 117VAC. If you short it, you short the 117VAC.
Bad idea. Look at the wiring diagrams in the above URL's.

What safety can this be providing any way?

A better question would be why are your bulbs burning out? It might
be that the safety features is actually doing its job and preventing a
meltdown. 2500 bulbs belches quite a bit of heat. Before you disarm
the safety features, do some calculating:

Each bulb burns about 1/2 watt. 2500 lights burn about 1250 watts,
most of which goes up in heat, not light. That's quite a bit of heat
that has to go somewhere. My guess(tm) is that your tree is
overloaded with lamps and they are blowing because they're getting too
hot.

Another possibility is that you're killing them with a light flasher.
The inrush current is perhaps 10 times the normal operating current of
the bulb. This inrush current happens every time you apply power to
the bulbs. If they can't handle the high current, they'll blow.

Any other ideas, aside from what we did last year - just throw a set of
lights on it, which defeats the purpose of paying the price for a pre-lit
tree?

Switch to Judaism. Our Hannukah menorah only requires 9 lights. If
that doesn't help, there are LED lamps, which burn far less power and
last almost forever. I bought a small string 2 years ago. They've
been on continuously for about 2 years and none have blown.

This is driving me and my wife insane.
Thanks in advance for your input.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Here's an update.

In tracking down and replacing numerous burnt lamps, The back half -
the side closest to the far end of the string - suddenly lit up.

What is strange is that I was working on the end closest to the plug
at the time.

Also, I have replaced all burnt bulbs with new ones that were tested
prior to installation. Now I have half a string that does not light
for no obvious reason.

Keep the thoughts coming . . . I'll keep playing with this as long as
my sanity holds out . . . ..

Thanks.


Put one probe in the neutral slot of the outlet, then pull the bulbs out one
at a time and check for mains voltage at one of the contacts. If you start
in the center you can figure out which direction the open is, and quickly
narrow it down. Keep in mind you might have multiple faults.

A better question would be why are your bulbs burning out? It might
be that the safety features is actually doing its job and preventing a
meltdown. 2500 bulbs belches quite a bit of heat. Before you disarm
the safety features, do some calculating:

Each bulb burns about 1/2 watt. 2500 lights burn about 1250 watts,
most of which goes up in heat, not light. That's quite a bit of heat
that has to go somewhere. My guess(tm) is that your tree is
overloaded with lamps and they are blowing because they're getting too
hot.



No way, incandescent lamps will work fine in environments hot enough to burn
the insulation off the wires. Unless the tree is on fire, heat will
absolutely not cause these lamps to fail. This is not rocket science, bulbs
burn out, connections in sockets get bad, series wired lights are notorious
for problems like this. Additionally, as each lamp fails and shunts, the
voltage across the remaining lamps increases and if left unchecked they'll
start to burn out too. More than once I've had this cascade in smaller
strings to the point that every lamp burned out until the fuse in the plug
opened.

"**THE-RFI-EMI-GUY**" wrote in message
...
Don't try to short out the safety bulb, or you will have a fire. It is
there to act as a fuse.

As the "shunt" bulbs burn out, the voltage (and current) accross the
remaining bulbs increases thus accelerating failure of remaining "shunt"
bulbs. Eventually the "safety" bulb in the string blows out. The solution
is to replace "shunt" bulbs whenever they blow out. Delayed too long, the
"safety" bulb goes as well.

I would string a new set of lights on the worst branches this year and
replace the tree next year for safety's sake.

2500 lights, thats a lot of lights!




When did this "safety bulb" thing come about? This thread is the first I've
ever seen or heard of it. Is it a European thing or is this here in the US?
Every string of miniature series lights I've ever seen has all identical
shunted lamps and a fused plug.

"James Sweet" wrote in message
news:KbQ%i.5554$B21.4712@trndny07...

"**THE-RFI-EMI-GUY**" wrote in message
...
Don't try to short out the safety bulb, or you will have a fire. It is
there to act as a fuse.

As the "shunt" bulbs burn out, the voltage (and current) accross the
remaining bulbs increases thus accelerating failure of remaining "shunt"
bulbs. Eventually the "safety" bulb in the string blows out. The solution
is to replace "shunt" bulbs whenever they blow out. Delayed too long, the
"safety" bulb goes as well.

I would string a new set of lights on the worst branches this year and
replace the tree next year for safety's sake.

2500 lights, thats a lot of lights!




When did this "safety bulb" thing come about? This thread is the first
I've ever seen or heard of it. Is it a European thing or is this here in
the US? Every string of miniature series lights I've ever seen has all
identical shunted lamps and a fused plug.

I bought very long strings in Walmart a few years back, as house decoration
lights are VERY expensive here in the UK compared to in the US. As each
'set' is made up of two strings, originally paralleled by the end-of-string
connectors for use on US 110v line power, it was easy enough over here to
just remove the plugs at one end and series two strings for 230v line power.
You could then just plug two more 110v strings, one into each 'far-end'
connector, to have two 110v paralleled strings in series with another two,
across atotal supply of 230v for 2000 lights. Total cost about $16 as I
recall. Over here, that amount of lamps would have cost $200 or more,
equivalent.

Anyways, the point is that these are a three wire circuit, and each new
three wire sub-string, has a replaceable safety fuse lamp at its beginning,
so there are multiple safety bulbs per fully wired string. So no, it's not a
European-only thing, as these are US purchased lights. Every year, these
ones drive me up the wall as well. Every year, I think that I've got the
wiring arrangement 'fixed' in my head, then every year, it all seems to go
wrong. The fact that I have paralleled strings in series, *really* confuses
the issue, because if one section of one string goes out on one series'd
half, then the voltage no longer divides equally across each paralleled
string, so one half lights up like flashlamp bulbs, whilst the other half go
as dim as candles ...

Arfa

On Nov 18, 12:36 am, "James Sweet" wrote:
"**THE-RFI-EMI-GUY**" wrote in message

...





Don't try to short out the safety bulb, or you will have a fire. It is
there to act as a fuse.

As the "shunt" bulbs burn out, the voltage (and current) accross the
remaining bulbs increases thus accelerating failure of remaining "shunt"
bulbs. Eventually the "safety" bulb in the string blows out. The solution
is to replace "shunt" bulbs whenever they blow out. Delayed too long, the
"safety" bulb goes as well.

I would string a new set of lights on the worst branches this year and
replace the tree next year for safety's sake.

2500 lights, thats a lot of lights!

When did this "safety bulb" thing come about? This thread is the first I've
ever seen or heard of it. Is it a European thing or is this here in the US?
Every string of miniature series lights I've ever seen has all identical
shunted lamps and a fused plug.- Hide quoted text -

- Show quoted text -

James,

Thank you for the information. I got this tree 5 years ago and this
is the first time I have seen this ""safety bulb" I no longer have
the directions to the tree, but will take a picture of this special
lamp and sent it to you.

It does look exactly like the other bulbs, except that it's base is
white and it is permanently installed into it's base, as if it were
molded in. Each layer of branches has its own string of lights; they
either plug into the previous string or into a main extension cord
that traverses the trunk of the tree. Each layer of branches/string
of lights has one of these bulbs.

On Nov 18, 7:26 am, "Arfa Daily" wrote:
"James Sweet" wrote in message

news:KbQ%i.5554$B21.4712@trndny07...





"**THE-RFI-EMI-GUY**" wrote in message
...
Don't try to short out the safety bulb, or you will have a fire. It is
there to act as a fuse.

As the "shunt" bulbs burn out, the voltage (and current) accross the
remaining bulbs increases thus accelerating failure of remaining "shunt"
bulbs. Eventually the "safety" bulb in the string blows out. The solution
is to replace "shunt" bulbs whenever they blow out. Delayed too long, the
"safety" bulb goes as well.

I would string a new set of lights on the worst branches this year and
replace the tree next year for safety's sake.

2500 lights, thats a lot of lights!

When did this "safety bulb" thing come about? This thread is the first
I've ever seen or heard of it. Is it a European thing or is this here in
the US? Every string of miniature series lights I've ever seen has all
identical shunted lamps and a fused plug.

I bought very long strings in Walmart a few years back, as house decoration
lights are VERY expensive here in the UK compared to in the US. As each
'set' is made up of two strings, originally paralleled by the end-of-string
connectors for use on US 110v line power, it was easy enough over here to
just remove the plugs at one end and series two strings for 230v line power.
You could then just plug two more 110v strings, one into each 'far-end'
connector, to have two 110v paralleled strings in series with another two,
across atotal supply of 230v for 2000 lights. Total cost about $16 as I
recall. Over here, that amount of lamps would have cost $200 or more,
equivalent.

Anyways, the point is that these are a three wire circuit, and each new
three wire sub-string, has a replaceable safety fuse lamp at its beginning,
so there are multiple safety bulbs per fully wired string. So no, it's not a
European-only thing, as these are US purchased lights. Every year, these
ones drive me up the wall as well. Every year, I think that I've got the
wiring arrangement 'fixed' in my head, then every year, it all seems to go
wrong. The fact that I have paralleled strings in series, *really* confuses
the issue, because if one section of one string goes out on one series'd
half, then the voltage no longer divides equally across each paralleled
string, so one half lights up like flashlamp bulbs, whilst the other half go
as dim as candles ...

Arfa- Hide quoted text -

- Show quoted text -

Arfa,

If you need more lights shipped over there, just send me an email
direct, tell me what you want, and I'd be happy to help you.

And thanks for your response to the post.

On Sat, 17 Nov 2007 21:10:54 -0500, "Reactor"
bruce.gettel-at-myactv.net wrote:

Hi All,

I have a pre-lit, 12', 5-year old Christmas tree with about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's not
a broken wire.

The first bulb in each section is a non-removable, non-shunt type bulb. The
directions say only that it is a safety bulb and cannot be replaced. On at
least one string, this safety bulb appears to be blown.

What gives here? I have shunt bulbs that are supposed to keep a blown bulb
from taking out the whole section, but yet they are all out. I have line
voltage all the way through the string, and yet no lights. And I have a
"safety bulb" that cannot be replaced, yet is blown.

What happens if I cut the safety bulb off (it's molded into its socket) and
twist the three wires together. What safety can this be providing any way?
Any other ideas, aside from what we did last year - just throw a set of
lights on it, which defeats the purpose of paying the price for a pre-lit
tree?

This is driving me and my wife insane.

Thanks in advance for your input.

Why not replace entire strings? Factor in the replacement cost of
your house, do the math, and then do the safe thing.

The shunt bulbs are designed to fail in a shorted condition. As each
bulb dies, the voltage to the others is raised by a small amount
causing them to be stressed more and shorten their life . . . so it
makes a lot of sense to keep up the replacements and not let several
lamps in a string die and then ignore them.

With 2,500 lamps you might expect a shunt or two to fail open in than
number. It isn't like they are designed to rocket science standards.

The safety bulb is there to fail when the current is high enough to
cause unacceptable heating in the dead shunted bulbs - keeping the
lamps from melting the plastic sockets. It serves as a fuse, so just
taking it out is not the thing to do - replacing it with a fuse might
work for a short time and still be safe, but you still have to keep up
the lamp replacements to keep the fuse from blowing.

What safety can this be providing any way?

Well, your still around to complain about it . . . must be doing what
it is supposed to - fail open and turn off the power to the string.
--
---- Posted via Pronews.com - Premium Corporate Usenet News Provider ----
http://www.pronews.com offers corporate packages that have access to 100,000+ newsgroups

On Sat, 17 Nov 2007 21:10:54 -0500, "Reactor"
bruce.gettel-at-myactv.net wrote:

Hi All,


This is driving me and my wife insane.


Too late.

If the safety bulb is blown, then it is no good, toss it and get a new
one.

wrote in message
...
On Nov 18, 7:26 am, "Arfa Daily" wrote:
"James Sweet" wrote in message

news:KbQ%i.5554$B21.4712@trndny07...





"**THE-RFI-EMI-GUY**" wrote in message
...
Don't try to short out the safety bulb, or you will have a fire. It
is
there to act as a fuse.

As the "shunt" bulbs burn out, the voltage (and current) accross the
remaining bulbs increases thus accelerating failure of remaining
"shunt"
bulbs. Eventually the "safety" bulb in the string blows out. The
solution
is to replace "shunt" bulbs whenever they blow out. Delayed too long,
the
"safety" bulb goes as well.

I would string a new set of lights on the worst branches this year and
replace the tree next year for safety's sake.

2500 lights, thats a lot of lights!

When did this "safety bulb" thing come about? This thread is the first
I've ever seen or heard of it. Is it a European thing or is this here
in
the US? Every string of miniature series lights I've ever seen has all
identical shunted lamps and a fused plug.

I bought very long strings in Walmart a few years back, as house
decoration
lights are VERY expensive here in the UK compared to in the US. As each
'set' is made up of two strings, originally paralleled by the
end-of-string
connectors for use on US 110v line power, it was easy enough over here to
just remove the plugs at one end and series two strings for 230v line
power.
You could then just plug two more 110v strings, one into each 'far-end'
connector, to have two 110v paralleled strings in series with another
two,
across atotal supply of 230v for 2000 lights. Total cost about $16 as I
recall. Over here, that amount of lamps would have cost $200 or more,
equivalent.

Anyways, the point is that these are a three wire circuit, and each new
three wire sub-string, has a replaceable safety fuse lamp at its
beginning,
so there are multiple safety bulbs per fully wired string. So no, it's
not a
European-only thing, as these are US purchased lights. Every year, these
ones drive me up the wall as well. Every year, I think that I've got the
wiring arrangement 'fixed' in my head, then every year, it all seems to
go
wrong. The fact that I have paralleled strings in series, *really*
confuses
the issue, because if one section of one string goes out on one series'd
half, then the voltage no longer divides equally across each paralleled
string, so one half lights up like flashlamp bulbs, whilst the other half
go
as dim as candles ...

Arfa- Hide quoted text -

- Show quoted text -

Arfa,

If you need more lights shipped over there, just send me an email
direct, tell me what you want, and I'd be happy to help you.

And thanks for your response to the post.

Thanks, Bruce. Kind of you to offer. I do get over to the US fairly often
( I will be in Vegas in a few weeks time ) so I usually take the opportunity
to stock up on stuff like this that I can't get back home - like Advil for
instance, or Bengay patches for my dear old mum's arthritic neck. Last time
I was there just before Christmas, I bought another whole set of lights.
They were literally about $5 in Walmart, and I got them just for the 500
spare bulbs it gave me ... Good luck with fixing your problem. Believe me, I
know how frustrating it can be, in my case, up a ladder, in the cold, with
it getting dark, and a pocket full of spare bulbs that keep slipping from my
frozen fingers !

Arfa

"James Sweet" hath wroth:

A better question would be why are your bulbs burning out? It might
be that the safety features is actually doing its job and preventing a
meltdown. 2500 bulbs belches quite a bit of heat. Before you disarm
the safety features, do some calculating:

Each bulb burns about 1/2 watt. 2500 lights burn about 1250 watts,
most of which goes up in heat, not light. That's quite a bit of heat
that has to go somewhere. My guess(tm) is that your tree is
overloaded with lamps and they are blowing because they're getting too
hot.

No way, incandescent lamps will work fine in environments hot enough to burn
the insulation off the wires. Unless the tree is on fire, heat will
absolutely not cause these lamps to fail.

True. Heat does not cause the lamp to fail, but does aggrivate the
problem. Although the author does not specifically mention the
obvious, the hotter the bulb, the faster the evaporation, and
therefore, the faster the failure.

http://members.misty.com/don/bulb1.html
How light bulbs burn out.

Due to the high temperature that a tungsten filament is operated
at, some of the tungsten evaporates during use. Furthermore,
since no light bulb is perfect, the filament does not evaporate
evenly. Some spots will suffer greater evaporation and become
thinner than the rest of the filament.

These thin spots cause problems. Their electrical resistance is
greater than that of average parts of the filament. Since the
current is equal in all parts of the filament, more heat is
generated where the filament is thinner. The thin parts also have
less surface area to radiate heat away with. This "double whammy"
causes the thin spots to have a higher temperature. Now that the
thin spots are hotter, they evaporate more quickly.

It becomes apparent that as soon as a part of the filament becomes
significantly thinner than the rest of it, this situation compounds
itself at increasing speed until a thin part of the filament either
melts or becomes weak and breaks.

This is not rocket science, bulbs
burn out, connections in sockets get bad, series wired lights are notorious
for problems like this. Additionally, as each lamp fails and shunts, the
voltage across the remaining lamps increases and if left unchecked they'll
start to burn out too. More than once I've had this cascade in smaller
strings to the point that every lamp burned out until the fuse in the plug
opened.

I haven't. There are usually 50 bulbs in series. When the Noma
"Stay-Lit" bulbs blow up, a roughly 5 ohm shunt ends up across the
bulb. With 50 bulbs, it would take quite a few bulbs to blow, before
the current would creep up to the point where the others might blow.
http://christmas.howstuffworks.com/christmas-lights2.htm
http://www.planetchristmas.com/Minis.htm
However, if your lamp string use some other method of maintaining
operation, such as shorting instead of introducing a 5 ohm shunt, then
it might blow the other bulbs.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Nov 18, 2:22 pm, Jeff Liebermann wrote:
"James Sweet" hath wroth:

A better question would be why are your bulbs burning out? It might
be that the safety features is actually doing its job and preventing a
meltdown. 2500 bulbs belches quite a bit of heat. Before you disarm
the safety features, do some calculating:

Each bulb burns about 1/2 watt. 2500 lights burn about 1250 watts,
most of which goes up in heat, not light. That's quite a bit of heat
that has to go somewhere. My guess(tm) is that your tree is
overloaded with lamps and they are blowing because they're getting too
hot.
No way, incandescent lamps will work fine in environments hot enough to burn
the insulation off the wires. Unless the tree is on fire, heat will
absolutely not cause these lamps to fail.

True. Heat does not cause the lamp to fail, but does aggrivate the
problem. Although the author does not specifically mention the
obvious, the hotter the bulb, the faster the evaporation, and
therefore, the faster the failure.

http://members.misty.com/don/bulb1.html
How light bulbs burn out.

Due to the high temperature that a tungsten filament is operated
at, some of the tungsten evaporates during use. Furthermore,
since no light bulb is perfect, the filament does not evaporate
evenly. Some spots will suffer greater evaporation and become
thinner than the rest of the filament.

These thin spots cause problems. Their electrical resistance is
greater than that of average parts of the filament. Since the
current is equal in all parts of the filament, more heat is
generated where the filament is thinner. The thin parts also have
less surface area to radiate heat away with. This "double whammy"
causes the thin spots to have a higher temperature. Now that the
thin spots are hotter, they evaporate more quickly.

It becomes apparent that as soon as a part of the filament becomes
significantly thinner than the rest of it, this situation compounds
itself at increasing speed until a thin part of the filament either
melts or becomes weak and breaks.

This is not rocket science, bulbs
burn out, connections in sockets get bad, series wired lights are notorious
for problems like this. Additionally, as each lamp fails and shunts, the
voltage across the remaining lamps increases and if left unchecked they'll
start to burn out too. More than once I've had this cascade in smaller
strings to the point that every lamp burned out until the fuse in the plug
opened.

I haven't. There are usually 50 bulbs in series. When the Noma
"Stay-Lit" bulbs blow up, a roughly 5 ohm shunt ends up across the
bulb. With 50 bulbs, it would take quite a few bulbs to blow, before
the current would creep up to the point where the others might blow.
http://christmas.howstuffworks.com/christmas-lights2.htm
http://www.planetchristmas.com/Minis.htm
However, if your lamp string use some other method of maintaining
operation, such as shorting instead of introducing a 5 ohm shunt, then
it might blow the other bulbs.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

I have a similar problem with a 9ft. prelit tree we bought 4 years
ago. Try flicking the safety bulb with your finger while the string
is plugged in. This has worked for us over the years, but I have one
string for which this technique no longer works. I'll figure out how
to repair it, then I'll update you with the answer unless you've
already come up with a solution. Let me know if you have.

On Nov 17, 9:10 pm, "Reactor" bruce.gettel-at-myactv.net wrote:
Hi All,

I have a pre-lit, 12', 5-year oldChristmastreewith about 2500 lights.
Entire sections (levels of branches, if you will) will not light. You can
imagine what it's like to search and replace burnt bulbs.

The bulbs are of the "shunt type" of course, but still, no lights. I have
good line voltage at the end of the string, so I am pretty certain it's not
a broken wire.

The firstbulbin each section is a non-removable, non-shunt typebulb. The
directions say only that it is asafetybulband cannot be replaced. On at
least one string, thissafetybulbappears to be blown.

What gives here? I have shunt bulbs that are supposed to keep a blownbulb
from taking out the whole section, but yet they are all out. I have line
voltage all the way through the string, and yet no lights. And I have a
"safetybulb" that cannot be replaced, yet is blown.

What happens if I cut thesafetybulboff (it's molded into its socket) and
twist the three wires together. Whatsafetycan this be providing any way?
Any other ideas, aside from what we did last year - just throw a set of
lights on it, which defeats the purpose of paying the price for a pre-littree?

This is driving me and my wife insane.

Thanks in advance for your input.

Bruce, I solved the problem on my tree. The "safety bulbs" appear to
be a "safety" for the manufacturer so the strings will all go out
eventually and force you to buy another tree. They are simply bulbs
without a shunt. I was able to pull the non replaceble white bulb
bases out of the sockets with pliers and dental picks and I replaced
the bulbs with ones that had shunts using the same white bases, and
everything works fine. If you can't get the white bulb bases out, you
could just cut the socket out of the circuit and splice the wires
together. The only result will be slightly brighter lights since
you've removed a little resistance form the series circuit.

Merry Christmas! Dish

wrote:

The only result will be slightly brighter lights since
you've removed a little resistance form the series circuit.

Merry Christmas! Dish

And that, of course, is the whole purpose of the safety bulb. When one
shunt bulb burns out, the shunt shorts it, and each remaining bulb gets
a little bit more voltage. When another shunt bulb burns out, it happens
again - and again and again. Pretty soon, there are only a few working
bulbs left, and the string is drawing more current than it was designed
to. The question then becomes which burns up next - the remaining bulbs,
or the wire connecting the bulbs.

Bill

"Bill Jeffrey" wrote in message
...
wrote:

The only result will be slightly brighter lights since
you've removed a little resistance form the series circuit.

Merry Christmas! Dish

And that, of course, is the whole purpose of the safety bulb. When one
shunt bulb burns out, the shunt shorts it, and each remaining bulb gets a
little bit more voltage. When another shunt bulb burns out, it happens
again - and again and again. Pretty soon, there are only a few working
bulbs left, and the string is drawing more current than it was designed
to. The question then becomes which burns up next - the remaining bulbs,
or the wire connecting the bulbs.

Bill


In my experience, one or more of the shunts does. They're a lot smaller than
the wire in the string.

On Dec 9, 5:49 pm, "James Sweet" wrote:
"Bill Jeffrey" wrote in message

...





wrote:

The only result will be slightly brighter lights since
you've removed a little resistance form the series circuit.

Merry Christmas! Dish

And that, of course, is the whole purpose of the safety bulb. When one
shunt bulb burns out, the shunt shorts it, and each remaining bulb gets a
little bit more voltage. When another shunt bulb burns out, it happens
again - and again and again. Pretty soon, there are only a few working
bulbs left, and the string is drawing more current than it was designed
to. The question then becomes which burns up next - the remaining bulbs,
or the wire connecting the bulbs.

Bill

In my experience, one or more of the shunts does. They're a lot smaller than
the wire in the string.- Hide quoted text -

- Show quoted text -

I replace my bulbs when they burn out, so I don't have the domino
effect predicted above. Reactor's strings probably have fuses in the
plugs like mine do, and like all fuses, they're designed to protect
the wiring. By the way, I love my prelit tree, it looks awesome and
is easy to keep functioning if you apply a little common sense.

Dish

In my experience, one or more of the shunts does. They're a lot smaller
than
the wire in the string.- Hide quoted text -

- Show quoted text -

I replace my bulbs when they burn out, so I don't have the domino
effect predicted above. Reactor's strings probably have fuses in the
plugs like mine do, and like all fuses, they're designed to protect
the wiring. By the way, I love my prelit tree, it looks awesome and
is easy to keep functioning if you apply a little common sense.

Dish


I do too, but on two occasions I've had it happen with a short 20 or 35
light string. I wasn't in the room, but within a period of a couple hours,
it cascaded until every bulb in the string was blown, about half of them
were blackened significantly and several had open shunts. I guess it's not
that surprising since all the bulbs had the same hours on them and once one
failed the others ran hotter and so on.

That said, no harm was done, and I've still yet to see a string with a
safety bulb in the first place so by putting a normal bulb in there you're
no worse off than someone using an older string without that feature.