LED lamp failure?

19 Jan 2005
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United Kingdom
Hi everyone

Going to look at some LED deck lights next week which the householder said are dim/flickering/sometimes go off (although not all of them at the same time).

I suspecting that it might be the lamps that are on their way out, rather than the driver? How do you test LED lamps? Continuity test as per incandescents??

Never tested these lamps before, but as they seem to be getting more popular it would be good to know


(Don't have any more info about the set up as yet as I've not been to look at them)
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If the driver isn't built into the lamp, a diode test (if your meter has that setting) should indicate a volt drop one way across the LED (may be in the region of 1-2v) and open circuit the other way.
As it is deck/outside lights I would suggest doing a standard check of all the wiring and connections on the 230v side first.

Its more likely to be a leaky box with no drain hole.
Thanks for replies guys.

Electronics - Not sure if my tester can do that test... (it's just the usual AC stuff)

Taylor - maybe but as some lamps are OK and others a bit dim intermittently didn't think of this immed.

I suppose I'd like to know if LED's fail (as incandescents ie either work or don't) or do they 'fade away'....

Cheers for ideas

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I suppose I'd like to know if LED's fail (as incandescents ie either work or don't) or do they 'fade away'....

I've certainly seen them fade over time due to overvoltage, although equally I've also seen them just stop working! It tends to be more of a problem when the LEDs are either overdriven, or were cheap taiwanese rubbish in the first place.
It's very unusual for an LED to show an intermittant fault. They tend to either work or not work. Once blown there is certainly no recovery.

I'd be looking at the wiring in this situation or like has been mentioned something getting wet. There could also be a problem with the connection to the actual LED inside the small enclosures assuming they are not sealed.
They can fail, they can flash, they can fade. It depends on where the fault is. It could be in the LED itself, or the driver, or the associated circuitry.

But surely you know this already? or are you hoping that all of us Brits will get on an airoplane and visit your exhibition?:p
While you're there, have a look at the power supply for the LEDs- if it is one of the cheap nasty 12v 60w ones designed for TH lamps then that will be causing problems (tried some cheap LED 12v GU10 replacements at work ages ago, in the Thorn fittings which had real transformers they worked well for a while but life wasn't brilliant due to overvoltage, in the Other fittings with external transformers they randomly didn't work or flickered or were pathetically dim).
While you're there...
One could infer from SB's absence for the last 10 months that she's very busy.

But surely she's not been so busy for the last 5+years that she still hasn't found time to go and look at these lights?
I think you missed the post this morning (from China) that has suffered from the Moderator's delete button.
Let"s leave this thread to slip away without another thought……
I guessed that something like that happened. But OBND's reply looked like it was to SB..
For advice on LEDs YouTube "clown science LEDs" and view big clives video explaining how LEDs work. FWIW I'd recommend a new set of lights.
We were told in Uni to test the idea of over driving LED's, but flash them on and off and as a class we all had to build the unit with 555 timer and relay chip and over drive them to destruction. What was a surprise was as we increased the current the LED reached a point where it started to reduce output before it finally failed. Once one had reached to point where the LED was damaged reducing current did not allow the full output to return.

We were using a light meter and we were convinced the light output had increased, but the meter did not show this to be the case. Thinking about it the meter would show the average light output where out eye may use the extra output and brain will compensate filling in the times when there is no light.

So in real terms it was how to measure light output as seen with the human eye rather than what the meter can read. This is nearly impossible to measure as each person will be different. The lecturer had read that flashing the LED allowed increased output and wanted to test it. However the results were disappointing.

My friend was using 320 mA LED's at 290 mA which resulted in them running a lot cooler this in turn allowed him to use a smaller heat sink. As to LED life it's hard to get data with so many variables temperature and current are both a factor with LED life and all it takes is for the sun to warm up a ceiling once or the voltage to rise above limits once for the LED to be damaged.

As the user we have no way of knowing how close to the limit an LED is being taken. The same lamps may last 5 years in one building and 15 years in another due to voltage and/or ceiling temperature.

It would be nice if price and quality went hand in hand but it does not. I have only just moved to LED so not enough time to tell, but with CFL I bought 16 Philips 8W lamps after 2 years most had failed, I replaced with 6 unknown make in one room and still all working 4 years latter. Other room replaced with LED.

It is clearly a problem for the electrical contractor, buying 500 lamps which prove not to last is very different to 16 lamps. And as to returning faulty lamps again a problem as how does the supplier know if they failed because faulty or failed due to too hot or massive spikes from machines in the same factory.

We as an industry need good will, so it does not really matter which are good and which are bad we have to buy well known makes to show the customer we are not cutting corners and any faults are not down to us.

Now some 5 years since the thread was started and nothing has changed. We have the good and bad all lumped together and no real way to work out which is which. Did my lamps fail because unlucky and got a faulty batch or due to Philips buying in from some factory in China who once the sample has been accepted drops the manufacturing standard.

Just not British hay what?

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