Christmas tree light circuit query

robgraham formulated the question :

We long ago swapped out all of the troublesome filament lamps sets for LED types.

The last so much longer and many have a selector switch, so you can get whatever mode of operation you want. One LED failing doesn't mean the entire set is out too.

Being old, I guess that the power supply is a conventional transformer. It could be that the thermal rating is so tight that it can't handle the continuous load of all 120 bulbs. The time constant will be such that it is OK whilst the flasher warms up, but might (or perhaps more accurately, the manufacturer won't guarantee that it won't) overheat if all the bulbs were left on permanently.

Chris

I've never seen a filament lamps set run from a transformer. They are usually just wired in series direct to the mains.

Wonder if the flashing ones have a smaller number of lamps - so leaving them on would shorten the life?

Being even older, the set will be direct mains operation (60 bulbs x 4 volts is the clue!!) I suspect that the fuse bulb cannot take the extra load - rearranging into two strings each with a fuse bulb - if you can get em might do what you want. otherwise do as I do, fit a power diode such as a 1N4007 inside the plug and the lights are only on for half a cycle which makes them last longer without, so it seems appearing much dimmer. two diode wired opposite ways round after the fuse bulb (suitably insulated!!) one of each string would also do the trick and keep them as a single plug/single fuse bulb.

Bob

And the bulbs are designed to blow short thus increasing the voltage on the others wich shortens their life until the current is great enough to blow the fuse bulb. Its was just a racket to sell bulbs in my opinion.

Brian

I don't believe that, maybe in that particular set the flaher is the fuse bulb? Brian

I have at least 4 sets running from transformers. Admittedly, they are some years old, but it became the norm, limiting the voltage the user could access to 24v.

There's one draped over a tree in my hall-way this very moment.

I have a set of exterior waterproof filament lamps that are about 6v 1W and run in parallel across a rather thick twisted green cable. One for each of four colours driven and a slightly thicker neutral return.

Possibly. The thing you have to watch with modern mains series sets is that they generally continue to work OK with one down but the dead one behaves as a short. So keep an eye out for unlit bulbs and replace them or you will get a much shorter life from the remaining ones.

Regards, Martin Brown

Two on my Christmas tree now, plus a couple of outdoor ones retired due to bulb failure and general dislike for maintenance in-situ ;-)

Chris

Each string needs a fuse bulb, presumbly the flasher acts in that capacity as well as flashing.

NT

Right. Short lived production? I went direct from the older series type to LED.

Do all of those filament types which are driven off a transformer include some form of sequencer to flash the lights? Ie, any just plain ol' on only types?

Hell, no. And even if had, I'd have removed it.

Thanks guys for your answers - this is a mains driven set. As Bob Minchin says the clue lies in the 60 x 4v in two parallel strings (=3D

I think I will approach this by bypassing the flasher and the existing fuse bulb with a switch and a fuseholder with a 200mA fuse in it.

Yes we should really get an LED system but the current system ain't broke yet so it won't get dumped.

Interestingly the only suggestion as to why the flasher bulb MUST not be replaced by an ordinary one is that the flasher bulb acts as a fuse

- then that is one fuse followed by another which is a bit weird.

Rob

Rob

I've got plain (non-flashing ones) ones.

Dave Plowman (News) laid this down on his screen :

The last couple of filament lamps set we bought, had a transformer, feeding a sequencing box, with a selector switch to select the actual sequence.

Right. Wonder if elfin safety meant series mains one were no longer 'legal'?

For some reason xmas lights wired on green speaker wire were sold decades after it had been banned for all other mains apps. Really nothing about those sets offered any robustness against direct contact to the mains.

NT