Most mini-light sets have an AC socket at the end to power a few other mini-light strings. The instructions usually say that at most 3 strings can be chained together. In practice, the 3A fuses in the plugs should handle loads up to 360 watts. So if the loads are 100-bulb 40-watt strings, one might think the fuses would handle 9 strings. But that would keep the fuses in the first plug pretty hot, and hot fuses are likely to fail. Limiting the load to 1A instead of 3A will keep the fuses cool, which takes us back to a 3 string limit.
LED strings can create longer chains, since they use about
One alternative to an endless chain of light strings is a tree of extension cords, each supporting a single short chain of mini-light strings.
Both fuses in the AC plug are needed send power into the string. If any part of a string lights, we know both fuses are good and do not need to be replaced. Both fuses are also good if there is power at the AC socket at the end of the string.
Running mini-lights without 3 amp fuses is extremely risky. These strings require 3A fuses because they use lamps designed to short out when they fail. And if all the bulbs short out, that would be a direct short across the AC line. The little fuses protect the wires, and that protects us.
Removing a bad string and re-stringing a new one can be more difficult than just fixing the string. And even a new string can fail.
Every time a bulb burns out and activates the internal shunt, the voltage increases across the other bulbs. The remaining good bulbs run hotter and fail sooner, with each failure further increasing the voltage on the other bulbs. The bulbs will fail increasingly quickly, especially the last 20, until they are all gone and finally blow a fuse. Allowing all the lamps to go will mean that it will take more just than a few replacement lamps to get the string going again.
Without some continuing maintenance, the natural process of bulb failure leads inevitably to blowing out every bulb in a circuit and one or both AC plug fuses as well. We can postpone the inevitable by replacing burnt-out bulbs. If we can keep 40 or 45 bulbs good in each circuit of 50, the worst case need never happen.
Mini-lights generally have 2 separate circuits. One circuit can go out leaving the other lit.
Regular blinking normally means a blinker bulb, or perhaps an electronic controller. Normally, mini-light strings have 2 or 3 independent circuits. A blinker bulb positioned anywhere in any of these circuits will cause only that circuit to blink. Blinker bulbs normally have a red tip, but apparently some do not, so we may not realize a blinker is in the circuit or where it may be. Close examination of the bulbs will reveal a blinker, since the inside of a blinker bulb differs from normal bulbs. Note that a string that has been blinking may have accumulated several weakened bulbs which may fail if allowed to cool to room temperature.
In a series circuit, a burnt-out bulb would normally darken the whole circuit. To minimize that, manufacturers include a "shunt" in each bulb, across the filament support leads. When the bulb burns out, a higher voltage appears across the filament leads, which causes the shunt to weld itself into place, which allows current to flow.
The shunt technology sometimes does not work. So when the bulb burns out, no current flows, and that circuit goes dark.
Normally, these strings have 2 power wires stretching from the fuses on the plug end, to the AC socket at the other. In essence, this is a fused mini extension cord, with 2 little wires good for only 3 amps.
Each lamp circuit consists of a continuous metallic connection from one of the power wires through sockets and lamps to the other power wire. One lamp circuit connects near the AC plug to one of the power wires, and then winds with the power wires to near the middle where it connects with the other power wire. The other lamp circuit starts near the middle and ends near the AC socket.
Most of the string has 3 wires: 2 AC wires and 1 lamp wire series-connecting 50 lamps at a time. But at the AC plug, the AC socket, and in the middle, there will only be the 2 AC wires.
The common string has a
Sure, if you are willing to rewire the system.
A single circuit typically has 50 bulbs in series, each connected
to the next with a single wire.
If we connect one end to one side of the AC power line through a
3 amp fuse, and connect the other end to the other side of the AC
line, we can eliminate the 2 wires which extend AC power.
In this way we can light a circuit of lights while eliminating
The mini-light series connections seem hard because they have very
different consequences than the parallel connections used in normal
The series connection allows little
In the series connection, exactly the same current flows through every lamp in the circuit. But the voltage across an individual lamps divides according to the resistance of each. When all bulbs in a circuit are similar, they all get the same voltage, even with wide manufacturing variations. But if some of the bulbs are manufactured differently, they may get too much voltage and blow out. The idea that bulbs need to be matched is much different than our familiar use of house lighting.
When replacing bulbs in a series circuit, even knowing the intended operating voltage is not sufficient. Bulbs operating at a particular voltage can produce a wide range of light depending on operating current and resulting power. Bulbs are designed for a particular current at a particular voltage. But the operating current may not be listed for replacement bulbs, or may not be understood if it is listed, because it is not needed for ordinary house or flashlight bulbs.
In these series circuits, the 120V line divides equally across