Christmas lights string keep blowing

[caphair]

I have a series-parallel incandescent style Christmas lights. The first string has gone out, I find a blown bulbs. The bulbs are rated at 2.5v .425w.

The only other bulbs I have around are rated at 2.5 .2w. I tried replacing the .4w bulbs with the .2w and when plugged in, lights flashed momentarily then went out again.

I now find that other .4w bulbs have blown and the .2w seems ok.

Could this have happened because of mixing the wattage? I figured the .2w replacement would have been brighter and the rest a little dimmer but still working.

Mixed bulbs issue or wiring?

[stj]

Re: Christmas lights string keep blowing

sounds about normal having to replace upto 6 lamps to get it running
!

[caphair]

Re: Christmas lights string keep blowing

Lol so mixing different wattage bulbs didn’t cause others to blow just a coincidence? Every time I replace found blown ones it keeps blowing again

[eccerr0r]

Re: Christmas lights string keep blowing

Now that I think of it, it is sort of a coincidence that had cause. It wasn't the different wattage bulbs, but rather the fact a lamp blew in the first place.

Remember all the bulbs in the string had the same MTBF from the factory so it's not unexpected a lot will blow around the same time so to speak...

[stj]

Re: Christmas lights string keep blowing

the biggest problem was the "self shorting" lamps designed to not blackout the whole string when they fail.
every failed lamp causes an increase in power to the remaining ones.
couple that with lazy people who dont fix it until several lamps are out and you see the issue.

[caphair]

Re: Christmas lights string keep blowing

So would have to keep replacing the ones that blow every time I power it on or just replace them all at once lol

[eccerr0r]

Re: Christmas lights string keep blowing

trouble too, can't see all the bad bulbs until one burns out on the side you see all the time...

I guess it's a good reason to throw out the whole string every season... or maybe flasher bulbs slightly increases useful life?

[caphair]

Re: Christmas lights string keep blowing

Yeah it sucks I was testing in continuity mode a lot of them.

So mixing different wattage bulbs is ok to do? Granted it might affect brightness but it wouldn’t cause other bulbs to burn out?

I have tons of the .2w bulbs and none of the .4w. I have to swap out the plastic bases to make them fit into the strings

[momaka]

Re: Christmas lights string keep blowing

Make a test jig so that you can test each individual bulb quickly.
Basically, take a socket that fits these bulbs and give it 2.5V from an adjustable power supply. Then take each bulb that appears dead and plug it in. If it lights up, it's good. If not, junk it.

That said, if you don't have an adjustable PSU to give 2.5V easily, then use a 5V adapter and connect 4x 100-Ohm 1/4 or 1/2 Watt resistors in parallel (or, alternatively, just use a single 25-Ohm 1 Watt resistor). Connect the parallel resistors in series with the socket for the 2.5V bulb. This should allow up to around 0.25 Watts to pass to the bulb @ 2.5V, so both the 0.2 Watt and 0.4 Watt bulbs should be able to light up and show if they are working or not.

I guess it's a good reason to throw out the whole string every season...

Yeah, unfortunately these things are too cheaply made to be worthwhile to repair (unless you are really bored or curious to do so.) Pretty wasteful when you think about it. I told my family to stop buying this junk long time ago. We still keep a few good strings that are better-made. (And some of the LED ones without any control circuits are actually quite decent.) But other than that, if they break, I just scrap them for parts (wires, plugs, and etc.)

[ChaosLegionnaire]

Re: Christmas lights string keep blowing

i see this is more corner cutting and planned obsolescence. they want u to keep buying a new led light strip from them every year during christmas to keep them in business! haha!

good call from momaka calling them out! and asking his family to stop buying those! lol! i'd do the same too!