Christmas tree lights

Our Christmas tree (3 years old) has 950 GE Constant On lights divided
into many strings. One string is out and I can't find a reason. The
Constant On lights are supposed to remain lit even if a bulb is
removred from a socket. I am at a loss as to how to troubleshoot the
problem as I don't know anything about the technology.

Can someone explain the technology for me and does anyone have any
troubleshooting techniques unique to this type of lights. ?

The other question I have involves a gadget I saw one night late
during a bout of insomnia. QVC was selling a Christmas light "fixer".
It seems if you have a string of lights out, you remove a bulb, plug
the end of this gadget into the empty socket, click the "trigger" a
few times and preato! the string is not lit. What is this thing and
how does it work ?

 

Well, the only two ways i can think of so that (remaining) lights
stay on if one is removed are:
1) All lights are in parallel and do are either rated for full line
voltage or there is a transformer driving them.
2) The lights are in sereis and the sockets are mechanically engineered
so removal of a bulb relieves pressure on a spring that then contacts
the other side (eg: the spring that contacts the solder "tip" of the
bulb would then short to the screw part).
**
Say what? The string does not work and using the "fixer" does nothing
(but take a byte out of your wallett)?

 

As you already suspected the one of the bulbs in the string burnt out.
Each of the bulbs have a low voltage insulating disk between two
contacts that are in parallel with the filament. When the filament
opens, the entire voltage appears across the disk and the disk melts
open and the contacts close. The burnt out bulb is now shorted. The
rest of the bulbs in the string operate ok but slightly brighter.

Sometimes when the filament opens, the insulating disk does not burn
open. That is the purpose of the "fixer". It momentarily applies a
much higher voltage across the series string (instead of 165 Volts peak,
the voltage may be as high as 250 volts). I do not think that the
"fixer" will work very well with a series/parallel configuration.

The solution is to remove and replace the bulbs in the 'dark" string
one-by-one with a known good bulb until the string lights up again.