My bathroom has four sconce light fixtures. The bulbs are quartz halogen with mini candelabra bases. Those bulbs don't last long, and replacing them is a royal PITA. (Getting the glass covers with their lousy screws off and on while standing on a chair and stretched over the granite counter.)

So I ordered some dimmable LED bulbs. Their claimed lifetime is quite long, but not infinite, and I wonder how they fail. Do they suddenly go completely dark? Or do they produce less and less light over time until you're annoyed enough to replace them?

I bought these:

https://www.amazon.com/gp/aw/d...=mini+candelabra+led

My guess is the electronics required to step down the 120V wall voltage to run the LEDs dies before the actual diodes do. I'd assume they just go out rather than dimming over time.

Mine started to flicker as though the heatsink was failing.

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My guess is the electronics required to step down the 120V wall voltage to run the LEDs dies before the actual diodes do.

I believe that's the case. I have had 14 Crees fail since I installed them in 2014.

Heat and poor QC.

They have driver/diode inside them that coverts 120vac to usually 12 or 24vdc. They have small circuit board that performs this function. The solder connections fails or the driver/diode fails, or both. Often times people fail to read the packaging and/or lamps and use them incorrectly.

Common warnings on lamps/packaging.

• Dry location only - no bathrooms or outdoors
  
• Do not use where directly exposed to water - damp location OK, outside/bath
  
• Not for use in totally enclosed fixtures - needs airflow to not over heat.
  
• Do not use with dimmers
  

Some don't like being installed upside down because heat rises and bakes the board.

Make sure yours don't say either "not for use in damp location" or "not for totally/fully enclosed locations"

Either way I would remove the glass and save to avoid excess heat.

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Some don't like being installed upside down because heat rises and bakes the board.

I have heard that before, but I have grabbed several of these lights at the base and none of them were even that warm to the touch.

What type of materials are they using that are susceptible to temperatures that aren't even uncomfortable to the human touch? And if that is the case, why not use something that is good to 150 degrees or so?

The ones I've had fail have gone out for a few seconds, then come back on, then gone out again, repeating this cycle. Like has been said, it's failure of the electronics, not the diodes.

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Originally posted by a1abdj:

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Some don't like being installed upside down because heat rises and bakes the board.

I have heard that before, but I have grabbed several of these lights at the base and none of them were even that warm to the touch.

What type of materials are they using that are susceptible to temperatures that aren't even uncomfortable to the human touch? And if that is the case, why not use something that is good to 150 degrees or so?

Not sure, I assume lead based solder. It won't get too hot until right before it fails. Feel one that is flashing at the base directly above the screw base and it will likely be warmer that other identical lamps. We are dealing with very small items here so the heat may not go through to wear you can feel it. Heat is also generated in different place than normal lamps. The LED emits very little and board won't til right before it dies.

Last question would be better posted to EE or manufactures. My guess is cost.

Thanks guys. I figured that if these LED bulbs lost luminance over time, the best strategy would be to replace all of them periodically – perhaps every three years. But there were no reports of luminance degradation in the preceding posts, so I'll just replace the bulbs individually when one of them begins to flicker.

Everything but the LED itself is what usually fails, due to cheap/shoddy manufacturing.

It's the Chineseium component.

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Originally posted by Pipe Smoker:
Thanks guys. I figured that if these LED bulbs lost luminance over time, the best strategy would be to replace all of them periodically – perhaps every three years. But there were no reports of luminance degradation in the preceding posts, so I'll just replace the bulbs individually when one of them begins to flicker.

They do loose brightness over time as well as change colors. The best bet is get one with high CRI (color rendering index). This the accuracy of the color they emit, the higher, the better the lamp. 85+ is good, 90+ is great, 95+ is phenomenal. The only relationship to longevity is the higher CRI lamps are better manufactured usually. Low CRI can result in different looking colors, especially if you buy two different brands or lots.

I bought one many years ago before they became common, about a 35 watt equivalent bulb (more like 15-20). Long enough ago that I paid about $35 plus shipping for it.

I left it on 24 hours a day since then. It had a couple dozen little LED in it. I just threw it away last week. It still worked, but many of the LED's had burned out, and it wasn't as bright anymore, less than say a night light bulb.

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Originally posted by sigmonkey:
It's the Chineseium component.

Damn that's funny, and likely carries an element of truth.

Seven years ago (yesterday, to be exact)we moved into this house. Within hte first few weeks I installed a red LED night light in the guest bathroom. Its still on, bright as ever. I forget the wattage, but it was low. All I wanted was a minor light source for late at night. I prefer to pee in semi-darkness. Its a caldelabra base. At the same time I installed an LED bulb by the front door. Its also a low wattage bulb, but standard base. Its also on 24 hours a day. Still burning good as new.

they got to make them as cheap as possible, or nobody would buy them. tradeoffs. cost vs quality.

To answer the question cheap components and heat. Some bad mojo with the lead free solder. There's a lot of stuff in the landfill because of lead free solder. Just ask Sony.

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Originally posted by a1abdj:
What type of materials are they using that are susceptible to temperatures that aren't even uncomfortable to the human touch? And if that is the case, why not use something that is good to 150 degrees or so?

If you look at really detailed datasheets for electronic components, they often have a little graph of MTBF (Mean Time Before Failure) vs. operating temperature.

You'll usually see something like a component with a rated operating temperature of 80 degrees C, but its MTBF doubles for every 10 degrees C you reduce the temperature below that.

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Originally posted by a1abdj:

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My guess is the electronics required to step down the 120V wall voltage to run the LEDs dies before the actual diodes do.

I believe that's the case. I have had 14 Crees fail since I installed them in 2014.

That is not good. I've got a couple dozen FEIT brand LED bulbs, that range in age from 3 to 8 years old, as I was gradually replacing incandescent with LED over that time. None have failed in that time.

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Originally posted by a1abdj:

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My guess is the electronics required to step down the 120V wall voltage to run the LEDs dies before the actual diodes do.

I believe that's the case. I have had 14 Crees fail since I installed them in 2014.

Unless you have a 1000 lightbulbs in your house, I'd seriously check your electric service.....voltage, neutrals, grounds.....etc.....

I changed all of the bulbs in my house to LED in Jan 2014.....I have a mixture of different brands.....I had one CREE fail and that's the only bulb that has failed in a light fixture that's on 16 hours a day.

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Originally posted by jimmy123x:

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Originally posted by a1abdj:

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My guess is the electronics required to step down the 120V wall voltage to run the LEDs dies before the actual diodes do.

I believe that's the case. I have had 14 Crees fail since I installed them in 2014.

Unless you have a 1000 lightbulbs in your house, I'd seriously check your electric service.....voltage, neutrals, grounds.....etc.....

I changed all of the bulbs in my house to LED in Jan 2014.....I have a mixture of different brands.....I had one CREE fail and that's the only bulb that has failed in a light fixture that's on 16 hours a day.

Generally, I'd tend to agree with this.

There was a batch or two or three that there have been reported failures with and they date to that time period though. The nice thing is they have a 10 year warranty, so the problem is easily fixed the bad part is I've heard you need proof of purchase to make a claim.