Old christmas lights

[Carol Anne]

We found a box of old decorations and lights in mother in law's loft, some of the sets of lights go back to the 40's 50's and are the large cone shape that even I can remember! Problem is I would love to have them on our tree this year instead of the modern ones as they have a lovely nostalgic glow, but I'd hate them to burn out and be gone for ever. Would lighting them up for only couple of hours at a time preserve the bulbs for longer or would it make no difference? any ideas welcome.

[woofgang]

I think its the surge of turning on and ?off that tends to blow bulbs, although as I remember, the older ones had thicker filaments so less likely to blow. DO get the plug and wiring checked. DO check for over heating when they are on and treat then like candles, don't leave unnattended as apart from the age of them, safety standards were a lot lower then!!

[burnhal]

particularly get the wiring checked- the insulation on wiring of that vintage is likely to crumble leaving bare wires.

[Carol Anne]

Four sets in all, were neatly stored in original boxes. Wirng looks as new, but yes I'll be very careful. They're just so pretty and colourful, I wonder why they ever stopped making them.

[qapmoc]

These must be the old type screw-in lamps, where the glass itself had the shape of things like acorns, Xmas trees , etc...etc.... and was painted to be a decoration even when it is off.

The life of a filament lamp relates to the applied voltage and if the voltage is lower the life will be much longer. What you could try is to connect two sets of lights together in series, this will make each lamp have only half its intended voltage, obviously the light output will be lower but it might still be enough to see the effects from the bulbs.
In series means - that one wire from the 1st set goes to the live supply, the other wire from the 1st set connects to one wire from the 2nd set and the other wire from the 2nd set goes to the neutral supply.

[Carol Anne]

Thank-you qapmoc, this works a treat and the lamps glow just as nicely and much cooler. Asked everywhere about the bulbs, but apparently ebay is about the only source, and people pay a fortune for them. I wonder if running them off a dimmer would have the same effect?

[Tim B]

Yes a dimmer would prolong their life. The dimmer the better.

[qapmoc]

Hi Carol, well, dimmer switches of the simple type that you buy for home use are not really a good idea for this, they work by reducing the amount of time that the power is on per cycle not the actual voltage level, this leads to a very on/off type of supply to the lamps and leads to a lot of thermal stress, you can see this if you put a dimmer switch to a very low setting the lamp seems to flicker a bit ?
To be honest, for home use anything which does dimming of the actual voltage levels would be very expensive.

[Tim B]

I disagree entirely qapmoc. By reducing the current through the light you have effectively lowered its operating temperature and thus extended its life. You're delivering chopped DC rather than full-phase ac, the mean current thus being lower. No matter that you can see a flicker on a very low setting, at normal operating parameters there is no problem.

[qapmoc]

Yes Tim but we are talking about a filament which has a fast response to the applied current not a heating element or something with a long thermal response time, the chopped AC (not DC) pulsing effect will cause the filament to expand and contract slightly at 50Hz, this will put a lot more mechanical stress on the filament which will reduce its life .

[Carol Anne]

Problem solved 3 sets of 12 are now 2 sets of 18 burning at 14v each lamp instead of 20v. Daughter's boyfriend soldered them very nicely and have a 1 amp fuse in the adaptor.