Help with some old fairy lights

[Mark84]

Hi all,

I purchased some old Russian fairy lights which I took to a local electrician to put a UK 3 pin plug on, I also think they re-soldered some parts. The lights have been working for some time now but every so often a bulb will blow when I plug them in, but I can live with that.

More recently though, a bulb will pop every time I plug them in so I haven't been able to get any light out of them for a while now as I've been using up a ton of these bulbs.

Could it be that the latest batch of replacement bulbs I bought were not very good? The bulbs I have been using are 'E10 MES 12 VOLT 2.2 WATT INSTRUMENT BULB' (picture attached). Or could it be something else?

I've attached some photos of the lights incase that helps?

Thanks in advance,
Mark

 

[duke37]

This is not up to modern safety standards.

If the bulbs are not identical, then the voltage will not be shared equally and the hottest one will go pop. You will need twenty 12V bulbs minimum and 25 or so would give less risk of a bulb blowing.

 

[Gryd3]

This is not up to modern safety standards.

If the bulbs are not identical, then the voltage will not be shared equally and the hottest one will go pop. You will need twenty 12V bulbs minimum and 25 or so would give less risk of a bulb blowing.

Looks as though there is only 17 of them, unless there are more outside the frame of the picture.
I can't think of a way to use that strip without adding more lights to it.

 

[Mark84]

There are in fact 18 bulbs. As far as I know, all bulbs are 12v.

Would reducing the plug fuse to 3amp help? Or would that just not power it?

 

[Gryd3]

There are in fact 18 bulbs. As far as I know, all bulbs are 12v.

Would reducing the plug fuse to 3amp help? Or would that just not power it?

The fuse will not 'limit' or 'regulate' anything... it's merely a safety switch that will turn the whole thing off if it ever tries to draw more than 3Amps... the downside? It won't turn on again until a new fuse is put in.
Only fix I can think of is a higher voltage rating for the lights, or additional lights being added to bring down the average the rest of the lights see.

 

[duke37]

A 3A fuse should be big enough to run 20 strings. To protect the flex I would put in a 1A fuse if you can find one.

A plug-in lamp dimmer is the easiest and safest way to reduce the string voltage.

A diode in series with the string will pass only half the waveform so will reduce the dissipation but this involves a lot of work to make a box for safety. A resistance could also be used but some means of dissipating the heat would need to be made.

 

[duke37]

As a resistance you could place a 40W bulb in series with the string and if this a bit dim, go up to 60W.

 

[Mark84]

As a resistance you could place a 40W bulb in series with the string and if this a bit dim, go up to 60W.

Thanks very much for the suggestions! I'll try them out and see what happens.