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.

--
Cheers
Dave.