LED Light Bulb Autopsy

by Ben N on April 27, 2016

It was bound to happen. I finally had an LED light bulb burn out on me.

LED lighting has gone mainstream. For some time now, traditional style light bulbs have been available at affordable prices, and the energy savings can be considerable.

My house has nearly all LED Lighting (Where there aren’t LEDs are specialty applications, like the light in my oven.) I’m using several different brands and styles of bulbs. Bulbs include floodlights, which are great for my “can” lights in my kitchen and living room, round bulbs for lamps, and LED tubes in the 4′ fluorescent fixtures in my garage.

When I got home from work last night, my wife mentioned that the light over our kitchen sink was flashing, and then stopped working.

I got up on the step-stool, removed the bulb, and replaced it with a fresh LED bulb that I had handy. But why had the original stopped working?

One little trick that I do is to WRITE the date of installation on the bulb with a permanent marker. In this case, the bulb had only been in use for about 18 months – FAR shorter than it’s potential lifetime of over 20 years. Of course, the light over the sink is the most-used light in the house. When upgrading from traditional to highly efficient lighting, it’s the very FIRST place a person should look to start saving energy!

When I first examined the bulb, the diffusion cover was already loose. I twisted it counter-clockwise, and the cover popped right off. Below that was the circuit board with 10 surface-mount LEDs. Since it’s a 10-watt bulb, it’s pretty safe to say that each LED is 1 watt. Amazing how much light can come out of these tiny yellow squares!

I removed the screws that held in the circuit board, and flipped the board up out of the way. It was still connected by the wires making the electrical circuit, but I could see below. Inside was a gray, rubbery, potting material, and I spied the corner of a circuit-board and a capacitor sticking out from it.

I snipped the wires to completely remove the circuit board and get better access below. As I did, the reflector fell out. This is a completely separate piece of machined aluminum.

Looking at just the base of the bulb, there really wasn’t anything else to inspect. The potting material is durable stuff. Even if I hit it with a hammer, the blow would simply bounce off. So, it looks like that’s the end of my tear-down.

My best guess is that something in the base of the bulb failed. Likely, one of the components that converts AC to DC. When I pulled the bulb out, the base of it felt pretty warm, even though the light hadn’t been making light for a few hours. Perhaps an internal component failed, due to heat, as the heat couldn’t dissipate well through the potting?

The upside of this particular light bulb design is that I COULD at least take it apart. The plastic diffuser was completely removable, as was the all aluminum reflector. I also looked again and realized the LED circuit board should come right off the piece of aluminum it was on. Sure enough, I pried with a flat screwdriver, and it came right off. Under the LED board was a little dab of heat transfer paste, just like in a computer, between the CPU and a heat sink. In this case, the aluminum plate and the reflector act as the heat sink for the LEDs. About half of this LED bulb could go right in my household recycling bin.

As for the new bulb, I wrote the date on the base with a marker before screwing it in. It makes me wonder when the next time I touch that bulb will be? If it dies as quick as the first one, it might be two years from now. If it lives up to it’s proper life-span, I might not think about it again until after my now five-year-old daughter has graduated from college.

Only time will tell. One thing I can say for sure is that in the mean time, it’s going to be saving me on my electric bill!

-Ben

PS: The Little Girl and I smashed open the base of the bulb and then cut and picked away at the rubber to see what was inside. I’m not much of an electronics guy, but what I see looks about right for converting AC to DC and DC to a different voltage. Take a look at the photos and leave a comment!

{ 1 comment… read it below or add one }

1 anil September 16, 2016 at 3:57 am

You can reuse the LED’s..
You can just connect one capacitor and a Resistor to decrease power of AC and directly run LED’s on it..

http://www.discovercircuits.com/PDF-FILES/ACLINEPILOTLED1.pdf

You can use the link and run LED’s right off AC.. Life times may differ but still dirt cheap and if it works you may be saving a lot of money..

Cheers from India,
Anil Kumar

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