Outdoor festive lights advice please!

[Nicos]

Apart from "bin them"...could any of you more technical grapes out there make any suggestions please?

We have outdoor lights which are 5 sets of 100 bulbs all in a row ( proper connections)
The lights in each set are in series.

We have gone through every single bulb and replaced the blown ones.

They were checked using one of these...



All 500 bulbs work...including each of the fuse bulbs.

BUT...when each of the 5 sets is plugged in individually none of them light up.

( banging head against the wall moment...yup, we've all been there)

OH decided to connect a normal spot light at the end of each set of 5 and the spot light lit up in each case.
So, there has to be electricity getting through...so why don't the small bulbs light up?

They were really expensive to buy, (even subsequent ones at half price) and they are only 6 years old.
And yes, they stay in the tree all year.

[Bigmallly]

That is a strange one Nic. As you say if the light at the end of the chain worked, you would expect all the others to.........Sorry, I am also at a loss as to why they don't work.
Bulbs checked & changed.
Fuses ok.
Power going to end of chain.
Yep...........I'm truly gazzumped.

[dogsbody]

OK this may not help but the box instructions for my sets (which are all still in the box!) makes the following suggestion:

1. Plug the light set into an electrical outlet via the transformer provided
2. Push each bulb firmly into the holder
3. Take a working spare bulb and starting from the first bulb in the chain insert the working bulb into each holder (sequentially I think they mean)
4. The set will light when you locate the defective bulb

The bulb tester may have missed the duff one?

Good luck!!

[Nicos]

Looks like we'll be checking all 500 bulbs again, but how strange that none of the 5 chains light up.

We've even checked the main plug at both the socket and plug end too as that was the common denominator.
And yes, other appliances work from the same wall socket.

It's a strange one isn't it???

[Nicos]

Bet it's something REALLY simple!!

[PyreneesPlot]

Mr PP (electrical engineer) says:

Is this a string of 100 x 2.5V bulbs, no transformer? If so :-
If a mains lamp in series with the string lights, this indicates that the string has a low electrical resistance. The likely cause of a low string resistance is an internal short in the string somewhere near the start.
The odd thing is that all the strings act the same way, suggesting a common mode failure; the only thing common is the testing of each lamp. The lamp tester in the picture is for 12V+ lamps, and you have lamps at around 2.5V. Could that be the problem - all lamps are blown, but gone short circuit?
Also check that the bulbs replaced are the right voltage.

[Kristen]

If you do the try-a-good-bulb-in-each-holder to find the duff one then start at the other end ...

... the only time I have done this it was the very last bulb that was duff, so clearly starting far-end-first will be better

[Nicos]

Hi PP

Many thanks to your OH...some very useful things to run through!

The bulbs are K1 mains voltage 2.5v from Noma. All the same.

The actual tester is this ( just found it)

with a 9v battery

some of the bulbs I checked didn't light up very much, but did work...I wonder if this is the wrong tester for that type of bulb???
Maybe the ones which aren't glowing very much should be replaced???

When they were on the tree, 2 of the strings still worked even when some of the bulbs had blown if that helps with the diagnosis????

I only have about 5 spare bulbs ...and about 20 fuse bulbs ( original order was sent with fuses instead of normal bulbs!)
Can I put more than 2 fuses in one chain???

[Nicos]

If you do the try-a-good-bulb-in-each-holder to find the duff one then start at the other end ...

... the only time I have done this it was the very last bulb that was duff, so clearly starting far-end-first will be better

Are you suggesting I remove all the bulbs and test each socket with a working bulb???

I thought the bulbs in situ always made up the circuit and if removed the current would stop???

[PyreneesPlot]

Mr PP -

The tester uses a 9v battery so should only be used with bulbs > 9V!. Fuse bulbs normally go short circuit and stop working, but the overall string keeps going. It's possible the bulb tester has damaged the bulbs. Hmm. If possible, rig up a tester with 2 AA or AAA 1.5V batteries and test again, to find bulbs that all light up with the same brightness. That's important, otherwise the ones that are bright will stop the others from lighting up properly; you might find that you can spot these if it's really dark at night.
Try to limit the fuse bulbs to two.
Being lazy, I'd wait 'til night and see if you can spot odd bright ones. Also double check the spares are marked up with the correct voltage, and/or compare the markings with an original one.
Rotten job. Good luck.
Gifi have a good range of LED strings at surprisingly low prices if you get too ticked off.

[Nicos]

Ah...OK...so wrong bulb checker!
..and maybe the odd rogue bulb from another set? ( bit strange a they are always kept separate...but worth checking as you say!)

I'll be thrilled if we can just get one string working!

Guess what we'll be doing when it gets dark!

[Nicos]

ooops! ...that didn't sound quite right did it!!

[Kristen]

Are you suggesting I remove all the bulbs and test each socket with a working bulb???

Sorry, no, you take a known-good bulb and replace the one in the first socket. If still not lighting up then take the bulb you took out and swap that for the one in the second socket. This only works if only one bulb is duff ...

[Patchninja]

If you get that lo working you'll be seen from outer space!!! Lovelovelove xmas lights!

[Nicos]

Ha!...thanks!

Not had a chance to sit down and fiddle with them yet!

We're pretty ecologically minded so won't have them lit too much...but I really do love seeing them lit!