Questions about Christmas "flasher" mini-lamps

[Travis Evans]

Is anyone very familiar with the Christmas mini-lamps that are placed in
a series string of Christmas lamps and flash the whole circuit of lamps
on and off? I'm curious if it's unusual for them to be rather
unreliable. Probably so, given how cheaply they're probably made, but
I was just wondering.

What I mean is that (in my experience, at least) at some point during
their lives (usually not after too long), they often get to the point
where when started cold, they will burn steadily and not begin
flashing, even after waiting many minutes for them to warm up. It's
only after I lightly tap the flasher lamp with my finger several times
that it begins flashing. Once it gets started, it will usually
continue flashing on its own indefinitely like normal until the next
time the set is unplugged long enough for it to cool down. Then I have
to repeat the procedure next time I plug it in.

When I was younger, I've also seen a couple of these behave in an
opposite manner: They would began flashing automatically when plugged
in after initially warming up like they should, but only for a certain
length of time (say, somewhere around 20-30 minutes), after which they
got "stuck" and no longer flashed (just stayed on steadily). Then
after the set was unplugged and allowed to cool sufficiently, the whole
cycle would repeat itself again when plugged back in.

My understanding is that they work by a bimetallic strip that closes the
circuit when cold and breaks the circuit when they heat up, causing a
cycle of flashing. It seems that the contacts somehow get stuck (or
maybe even melted?) together easily and just burn steadily as a result
unless they're jarred loose again. Would this be a likely cause of
this behavior?

Another interesting I've noticed is that unlike the regular lamps on the
string, the inside glass of almost every flasher lamp I've seen
blackens very quickly--perhaps after only a few tens of hours or so of
operation.

 

[TKM]

Is anyone very familiar with the Christmas mini-lamps that are placed in
a series string of Christmas lamps and flash the whole circuit of lamps
on and off? I'm curious if it's unusual for them to be rather
unreliable. Probably so, given how cheaply they're probably made, but
I was just wondering.

What I mean is that (in my experience, at least) at some point during
their lives (usually not after too long), they often get to the point
where when started cold, they will burn steadily and not begin
flashing, even after waiting many minutes for them to warm up. It's
only after I lightly tap the flasher lamp with my finger several times
that it begins flashing. Once it gets started, it will usually
continue flashing on its own indefinitely like normal until the next
time the set is unplugged long enough for it to cool down. Then I have
to repeat the procedure next time I plug it in.

When I was younger, I've also seen a couple of these behave in an
opposite manner: They would began flashing automatically when plugged
in after initially warming up like they should, but only for a certain
length of time (say, somewhere around 20-30 minutes), after which they
got "stuck" and no longer flashed (just stayed on steadily). Then
after the set was unplugged and allowed to cool sufficiently, the whole
cycle would repeat itself again when plugged back in.

My understanding is that they work by a bimetallic strip that closes the
circuit when cold and breaks the circuit when they heat up, causing a
cycle of flashing. It seems that the contacts somehow get stuck (or
maybe even melted?) together easily and just burn steadily as a result
unless they're jarred loose again. Would this be a likely cause of
this behavior?

Another interesting I've noticed is that unlike the regular lamps on the
string, the inside glass of almost every flasher lamp I've seen
blackens very quickly--perhaps after only a few tens of hours or so of
operation.

You are correct. Some string sets have electronic flashers; but those also
have a control box of some sort in the circuit. The usual flasher is a
thermal element mounted in what looks like a lamp that fits into one of the
lamp sockets. Such devices have wide tolerances so the flashing cycle will
vary depending upon temperature, voltage, etc. Contacts can easily sputter
and stick. The dark deposit that you notice is likely the sputtered contact
material thrown off by the small arc that results when the contacts open or
close.

Terry McGowan

 

[Clive Mitchell]

My understanding is that they work by a bimetallic strip that closes
the circuit when cold and breaks the circuit when they heat up, causing
a cycle of flashing. It seems that the contacts somehow get stuck (or
maybe even melted?) together easily and just burn steadily as a result
unless they're jarred loose again. Would this be a likely cause of
this behavior?

Another interesting I've noticed is that unlike the regular lamps on
the string, the inside glass of almost every flasher lamp I've seen
blackens very quickly--perhaps after only a few tens of hours or so of
operation.

The bi-metalic flasher lamps arc slightly each time they open and close,
this can cause both pitting for a bad connection and welding of the
contacts together. It also has the slight blackening effect.