Replace failed LEDs with normal diodes in Christmas lights?

[c128]

Hi,

I have 3 sets of connectable Christmas lights that I usually join together, but this year one set has failed:

http://www.castlegatelights.co.uk/l...nnectable-red-led-outdoor-lights-p11251#11351

...the sets are no longer available, and the LEDs are soldered and sealed in place.

It looks like 3 bulbs in the set aren't working at all, whereas the others in the set light, but very dimly. It don't think it's a wiring issue, and I get the same result whether the set is plugged into one of the other sets or straight into the main connector; the other sets are fine. A tag on the wire of each set lists "LED data: 0.04W, 1.8-2.1V"

To be honest, I'm not particularly worried about 3 lights being out in the problem set, if the others worked.

With the above in mind...and seeing as these are external and I want to make a nice weatherproof seal...is there any reason I can't just hard replace the 3 bulbs that have failed with normal diodes rather than LEDs? I guess I'm assuming (perhaps wrongly ) that doing this with an appropriate diode would avoid impact on the other lights versus complete removal.

 

[NewOrder]

If they are wired in series, wouldn't putting a diode in a place of an LED then increase the voltage going to all the other LEDs those shortening the life?

 

[Spark123]

The short answer is no, a diode (bog standard silicon) drops around 0.7v forward biased. Your LEDs are around 2v. It would be possible to drop 2.1v by using 3 diodes in series.
Without seeing how the LEDs are connected and the PSU info it isn't possible to say how they can be fixed.

 

[c128]

Ah, mmm...thanks.

The PSU is only marked as 250V 3A. No more detail, but it's this:

http://www.castlegatelights.co.uk/l...able-for-kontsmide-connectable-set-p7730#7731

http://www.buykonstsmidelighting.co...nstsmide-4519-LED-System-Power-Cable_220.aspx

...the LEDs are wired in series within each set. There's also a black tube wired between the last 2 LEDs before the following set.

Added later:

Here's a picture that shows the wiring and the black tube:

Untitled

• c128
• 14 Dec 2013
• 1

 

[bernardgreen]

If you are going the trouble of replacing the dead / suspect LEDS with three diodes per dead LED you might as well buy LEDs of the same colour and replace LED with working LED.

As mentioned if you replace with a single diode the other diodes will likely be over volted or over current and will fail soon. The fact that 3 have failed suggest the strings are designed to run the LEDs close to maximum safe limits.

 

[c128]

If you are going the trouble of replacing the dead / suspect LEDS with three diodes per dead LED you might as well buy LEDs of the same colour and replace LED with working LED.

Well, that wasn't my original plan - hence the question.
But, yes, if it's 3 diodes per LED then that does seem silly .

The LEDs on the string are as in the picture - they're stamped DMC but are sealed with the wires inside, so I'm assuming I won't find a like for like replacement. Also, I'm not much bothered about what the three replacements end up looking like, seeing as I was going to get rid of them anyway - I just want the whole string back in service.

So - given what I know about the sort of LEDs I'm looking for (which is basically all that's on the string label - "LED data: 0.04W, 1.8-2.1V"):

* Am I just looking for any old LED for replacement that fits the listed voltage range?
* If not, is there more I can determine with a multimeter that might pin down the details of what I need as adequate replacements?

Thanks

 

[ban-all-sheds]

...the sets are no longer available, and the LEDs are soldered and sealed in place.

That's where you went wrong.

 

[c128]

...the sets are no longer available, and the LEDs are soldered and sealed in place.

That's where you went wrong.

Yep . Konstsmide were (are, I'm just unlucky?) a reasonably good brand, I thought; I'd seen the local council using the same connectable sets for their own lights, so thought they had some legs. As it stands, this strip has only lasted two Christmases - so ~4 weeks of use for 6 hours a day in total. Then again an LED can just go "pop" regardless, I guess...

 

[bernardgreen]

* Am I just looking for any old LED for replacement that fits the listed voltage range?

Basically yes, any old LED element of the same ( or very similar colour ) in a clear transparent plastic body should work. Some LEDs are a ultra violet emitter with the UV making a phosper glow. These may have a voltage higher than the LEDs being replaced and while they may work the other LEDs may be dimmer.

 

[mattylad]

Before you take them apart - take note of the way around they are wired by looking through the clear plastic in them.

 

[c128]

Thanks all for the input .

I have some 10mm red LEDs (clear body) on the way from Ebay with a matching voltage.

The main problem I'm going to have is sealing them under the base at the point the wires are soldered... Was thinking of just creating a small cylinder around the bottom of each (out of...something) and then filling with epoxy, but that doesn't sound ideal - heat-shrink won't cut it, and amalgamating tape would be too fiddly.

Not too bothered about how it looks, more concerned with the seal - any suggestions?

 

[ban-all-sheds]

Clear silicone?

 

[c128]

Clear silicone?

Oh, yeah, much better option - have some kicking around (assuming it hasn't gone off).