"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