Grumble, grumble - E12 lamp sockets

[David]

We have a set of out door lights - a string of (12V * 20) E12 lights in series giving 240V and running off mains electric. No transformer required.

Having just tested the bulbs of an out door light set with a meter (continuity beep) and sorted out 24 working ones (using some spares and some from a second set) then a day later seen a couple of the lights out but the string still working made me ponder.

The instructions say that with a lamp out the string will still work, but that you should change the bulb a.s.a.p. to avoid long term damage.

So presumably when the filament fails there is some kind of continuity pass through in the base which keeps the string alive.

However if this is the case then a bulb can pass the "beep" test but not light.

Cue the memory of the childhood hobbyist things where you had a battery and a light bulb and some circuitry. Often screwed to a bit of fibre board.

The sockets and bulbs I remember were almost certainly E12 and they just seemed to be an everyday thing.

Now I am looking for an E12 socket to wire up a simple bulb tester.

eBay lists them but the seem to come from China. No UK stockists.

Just grumbling and feeling old because things weren't like that when I were a nipper.

I will wander down to the oldest electrical shop I know in town, in case they have one in stock, but it may well be cheaper just to stock up on spare bulbs.

Cheers

Dave R

[Dave Plowman (News)]

The bulbs are designed to fail short circuit. So in a series wired configuration the rest still work - but at a higher than rated voltage. Hence the need to fit a new one ASAP.

Standard mains fairy light practice for probably 60 years.

[David]

Hence the need for a bulb tester which lights the bulb up, instead of a continuity tester which will still "pass" a failed bulb.

I blame these little low voltage twinkly things - back on the day everyone had 240V fairy lights and all the bits were common.

Cheers

Dave R

[Brian Gaff]

Are you sure that these like those old fashioned xmas lights don't just blow shorted out, making all the rest run a bit hotter until it reaches a point where the whole lot goes bang. What I used to do with those sort of lights was add a couple more into the chain so they were all running at a slightly lower voltage and it worked for years and years. Brian

[Dave Plowman (News)]

Or measure the resistance. A failed one will be near zero ohms, a working one very much higher. Measure a good one to get the actual figure.

But LEDs tend to have a much longer life. And safer, too.

[Andy Burns]

Presumably you don't care if it's batten or pendant?

[ARW]

What do you intend to use to power the bulb tester?

You need a shunt incase the lamp you are testing is in short circuit mode. Although I would pobably just use a cheap PP3 battery to do the test:-)

[David]

Cheap PP3 battery - I've ordered a connector with wires to add to the lamp holder.

Just need a bit of floorboard and a few nails and it'll be back to 1950s DIY.

Just off to heat the soldering iron on the gas stove.

Cheers

Dave R

[ARW]

I think you are overengineering it by adding lamp holders and battery connectors;-))

I was thinking more of just touching the lamps terminals onto the batteries terminals by hand.

[David]

Yes, probably over engineering.

Just have memories of lamp testers (they used to have them in electrical shops as well IIRC) where you screwed (or pushed) the lamp in and saw it light.

Carried away recreating memories.

Cheers

Dave R

[ARW]

I am not that old:-)