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.
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