Christmas lights not working

Hello,

My father-in-law bought some "icicle" lights last Christmas. He has come to use them this year and some of the icicles are not lighting, so he's given them to me to fix.

I don't know the make or model for sure. The label on the lights says "Konstsmide", so I am pretty confident that that is the make, yet the transformer says "Premier", a rival manufacturer. This could be the reason they have blown: he could be using the wrong transformer! I've emailed both companies and we will see if they reply.

There is a chain of plastic icicles and inside are up to six tiny filament lamps which light with the usual filament yellowish white. A section of sixteen bulbs is not lighting up; the rest work perfectly. The lights are always on: there is no flashing, sequencing, etc.

The (wrong?) transformer says it has an output of 24V AC. Since the working bulbs look "about right", I think that even if the transformer is the wrong one, by coincidence it might be outputting the correct voltage.

I have dismantled the icicle "lamp shade" and found a blown bulb. If I short this out, the other fifteen bulbs come to life. If I put an ammeter in its place, it reads 68mA AC. So far, so good.

It's a while since I was at school, so can someone just double check my maths: 24 Volts across 16 bulbs, would mean the voltage across each bulb is 24/16=1.5V. Is that right?

The reason I hesitate is that I have searched electronics catalogues and I cannot find any filament bulbs rated at 1.5V.

I don't want to just short the blown bulb because that will cause the current through the other bulbs to be 16/15ths higher and that in turn could cause more to blow. If I've got my maths right, the resistance of each bulb is twenty-something Ohms, so I might put a 22 Ohm resistor in its place if all else fails.

Does anyone know of a source for these tiny bulbs?

On a similar note, SWMBO wanted to follow the family tradition so we bought LED lights. The first year two sets went back because rain got into them. There is heat shrink over the LED and series resistor and you could see through the heat shrink that there was rust. We bought a different make last year but one or two LEDs are not working on that; again rust seems to be the problem. So much for LED lamps not needing replacing!

Thanks, Stephen.

Reply to
Stephen
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Your conclusions are about right. It sounds like the bulbs you need are

1.5v, 0.1w. Woolworths (sadly no longer in existence) used to sell packets of spare bulbs for Christmas tree lights - but you can probably still get them at electrical - or even pound - shops, etc.

If you do resort to using a resistor, its value probably needs to be slight higher than you calculated. If all 16 bulbs had been there, the current would have been 15/16 of what you measured - i.e. about 64mA rather than 68 - which implies a bulb resistance (when hot) of about

23.5 ohms.
Reply to
Roger Mills

May be just me but aren't xmas lights supposed to fail after one xmas?

and shouldn't a set of 4 spare bulbs cost almost as much as the original set of lights?

And of course last years bulbs won't fit this years new lights

And they have even taken to glueing the bulbs into the holders to stop me taking last year's working bulb and fitting it into this year's holder

Regards

Reply to
TMC

Not noticed you here since your "ducts" question the other week, did you get any further tracing where the cable goes after it leaves the village

- I presume you saw my replies to that thread?

Reply to
Andy Burns

We get all our spare bulbs in the Garden Centres. Most seem to stock them at this time of year along with myriad lighting sets.

Reply to
Tinkerer

The problem is that these are soldered in, so they are not expecting the customer to replace the bulbs, so the bulbs don't seem to be readily available anywhere.

The closest I found after much internet searching was a "rice grain" bulb rated at 1.5V but only 15mA

Thanks, Stephen.

Reply to
Stephen

You are quite right. I had allowed for the 15/16ths and it came to about 24 Ohms, I rounded it down because I was thinking standard resistor sizes were 22 and 27 Ohms.

Thanks, Stephen.

Reply to
Stephen

In practice, there is likely to be a tolerance of 10% or so either side of the nominal value. If you want to protect the other bulbs it may be advisable to err on the high side.

Reply to
Roger Mills

I was going to use two 47R in parallel but may be I should use 27R just to be safe. OTOH I don't want these to look dimmer than the rest. No joy looking for a bulb, so I think it will have to be a resistor.

Reply to
Stephen

So despite not knowing what youre talking about youre accusing your supplier of doing wrong and hassling them about stuff thats not their concern.

The value of the resistor is far from critical.

NT

Reply to
Tabby

Reply to
Stephen

Are you replying to the wrong post or have you just not read it properly? You are the one who appears not to know what they are talking about.

I don't have a "supplier". The lights in question are not even mine.

Notwithstanding that I don't have a supplier, I have not accused them of doing anything wrong.

I have not hassled anyone. I emailed two lighting companies to ask if they sold light bulbs, which seems perfectly reasonable to ask a shop that sells lighbulbs if they sell a particular bulb.

Too low and the lights will blow; too high and they won't come on at all.

Reply to
Stephen

I read your post fine. Good luck.

NT

Reply to
Tabby

Thats what I thought?

Reply to
The Medway Handyman

If you get cheapy sets from discount places that's the idea. B-)

Our main tree light set is now 11 years old, still going strong and I can still get spare bulbs in bags of 20 plus a fuse bulb for =A34.50. Normally replace two or three a year.

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Reply to
Dave Liquorice

Not really. If there are 16 bulbs in series, replacing one with a dead short won't immediately cause the others to blow: the expected effect would be roughly to halve their lifetime. It's the principle on which 'permanent contact' Xmas lights work; if a bulb fails a fusible material (effectively) shorts it out. You're always recommended to replace the failed bulb as soon as possible, to reduce the time for which the others in the chain are overrun, but it's not critical.

Replacing the blown bulb with a resistor is sensible, but don't waste time worrying whether to use 24R or 27R!

Richard.

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Reply to
Richard Russell

Nope I have put it on one side for now

Reply to
TMC

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