Hi Martin,

Richard here in NZ.

I'm pretty sure that the bulbs were 12V with ~20 in a string (at least
early on). Every year it was 'hunt the faulty lamp' game as at least one
bulb will have died or at least unscrewed itself. Later bulbs had a spring
loaded bypass so that when the filament died the spring tension would short
the bulb out and the remaining bulbs would light (with slightly increased
brightness). You could then easily see which had failed & replace it.
And  the flasher bulbs as you describe  also became available.
Later strings had more bulbs so the individual bulb voltage was less. The
connection method also changed from a scew - in type (like a panel lamp
fitting) to a miniature screw version, to a push fit.
All versions had the added excitement of being able to trap some conductive
tinsel and expose most of the tree to live @ up to 230V or so. It didn't
really bother us for some reason, you just had to be a bit careful when
changing a bulb.

RP



On Sun, 27 Jan 2019 at 17:17, Martin McCormick <martin.m@suddenlink.net>
wrote:

>         The last outdoor Christmas lights came down at our house today
> and I thought of a question as I was taking them down.  In
> countries where the AC line voltage is 120 volts on a standard
> circuit, one very common configuration is 35 incandescent bulbs
> in series.  The painted glass envelopes look much like NE2 neon bulbs but
> they are actually 3.4 volt incandescent lamps much like 2-cell
> flashlight bulbs with each bulb drawing a bit over 400 milliamps.
>
>         I am sure that there is cut-throat competition to
> manufacture the strings as cheaply as possible and still pass
> safety requirements in the various countries so my question is do
> they sell the same configurations only with 6-volt filaments in
> 240-volt countries or do they simply sell 70-lamp strings instead
> of 35-lamp strings as the minimum number of lights in one string?
>
>         Here, you can buy these lights with 70 or more bulbs but
> they appear to be 35-light series strings parallelled .  There is
> frequently a clear extra bulb with a red tip containing a
> thermocouple switch which causes the whole string to blink if you
> want it to.  70 or more light strings would need one blinker bulb
> per series string.
>
>         Each lamp contains a shunt that falls in place when a
> filament burns out so one still sees light from the remaining
> working bulbs but lots of luck if one of the sockets becomes
> intermittent as the whole string goes dark.  A capacitively
> coupled probe might tell you where the break is but a new string
> usually fixes the problem much faster.
>
> Martin McCormick WB5AGZ
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