responding to http://www.homeownershub.com/mainten...il-733988-.htm
DA wrote:
Joe Mastroianni wrote:

But, what causes CFL bulbs to fail?
In my experience CFLs fail so rarely that I was never interested in why and never investigated - always looked like a random event anyhow.

And, what causes LED bulbs to fail?

LEDs, on the other hand, failed so frequently that I did look and, basically, the reason is two-fold. They require bringing the voltage across each individual LED to 3.5-3.6V Given that you start out with 120V power, they string 20+ of them together so the power supply of the LED bulb does not have to lower it down too much and they also very frequently skimp on the design and the components of the power supply. I can't say for the higher-end LED bulbs which I've not yet gotten any due to costs and my general skepticism about their life expectancy, but the lower-end ones I've opened often even lack some component that are clearly labeled on the PCB inside. For example, an inductor that's intended to limit the inrush current through the string of the diodes, is often labeled on the board but missing (replaced by a wire short) because it's kinda expensive (about $1). I'm also pretty sure the LEDs themselves and every other component inside were picked from the lowest cost (lowest quality) bins.

One other intrinsic issue with LEDs due to their low voltage and consequent stringing of a couple of dozen together is that life expectancy of such serial circuit drops dramatically. It's pretty much false advertising when they print on the box "30,000 hours life" because even if one LED might really last 30,000 hours, the probability of the string of 24 failing in the first 1000 hours or less is much higher - the probabilities of each LED failing compound and bring the entire circuit's way down.

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