Well the danger was that the fuse bulb blew and people put in an ordinary
bulb, that was how you got runaway failure. In my experience the magic
number was around 6, at that point the next one to blow vaporised
internally, saving the rest!
However the rest were then weakened and for the rest of the Christmas you
were eternally replacing bulbs.
Brian

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"Dave Liquorice" wrote in message
idual.net...
On Tue, 17 Dec 2019 07:46:39 -0000, Brian Gaff \(Sofa 2\) wrote:

If you will recall back in the days of filament bulbs all wired in
series across the mains,

Not a lot different now, have chains of LEDS across a supply of a few
tens of volts.

Of course the danger here was that if a bulb blew short circuit then
you could get a wonderful catastrophic failure ...

Tree light bulbs are designed to fail short circuit. I've never known
a set run away blowing bulbs or the fuse bulb. Failing short makes
finding the duff one fairly easy, it's the one that isn't lit. Fail
open and you have to test each bulb individually.

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Cheers
Dave.