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Coincidence, or not? LED; Theory or Conspiracy?
Posted by: Buzz
Date: April 15, 2019 04:48PM
Rebuilt an old hanging swag lamp, and after a couple of days back in service, strange things happened. Lamp itself had been used for many years w/ a halogen bulb, and an incandescent rated dimmer. A few years ago the dimmer was replaced w/ a LED rated dimmer and the halogen bulb was replaced w/ a LED bulb. Original goal was to replace the shade, but when tearing the lamp apart, it was decided replacing the socket was in order, too.

After the rebuild was complete, I put the old LED bulb back in, and plugged the lamp back into its dimmer. Lamp worked fine for a couple of days, then bulb died. Took similar wattage LED bulb from other lamp on other side of room which was hooked up to its own LED rated dimmer that was purchased at same time as hanging lamp's dimmer; one is white, the other is black, because the controls are next to each other on the same nightstand, so it makes it easy to tell which dimmer is for which lamp. The bulb from the working lamp then also sorta worked in the rebuilt hanging lamp, but it made a nasty humming sound that varied its pitch and intensity in conjunction w/ sliding the dimmer control. Reversing the plug didn't help. Putting the noisy bulb back in its original lamp quieted it back down and it resumed working fine.

FWIW, both LED bulbs were the expensive variety. Next, a new Costco cheapie 100W LED bulb was placed in the rebuilt hanging lamp, and it works fine. No humming, though it does exhibit a common (for us anyway) LED behavior of needing a fair amount of juice to power on, before the light comes on and the dimmer takes over, and it needs to be powered up to around 75-80% power before the dimmer will dim the bulb to its lowest setting. The old (now dead) LED bulb worked more fluidly w/ the dimmer from initial power on, and throughout the entire power cycle.

Is it a coincidence that both expensive LED bulbs had issues w/ the rebuilt lamp? Or is there something I should look into w/ the lamp and/or dimmer? Basically, my gut says it's gotta be something w/ the bulb(s) or dimmer, but for one bulb to die, then another start to hum, back to back, makes me want to look towards the grassy knoll for another possibility.
Any ideas? Thanks.

Don't want to reach for another expensive LED bulb until there's a valid explanation, or two, available.
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Re: Coincidence, or not? LED; Theory or Conspiracy?
Posted by: space-time
Date: April 15, 2019 04:58PM
I am not quite sure I understand all the details, but the lamp at this point is just a dumb appliance, the dimmer is external and the LED is mounted in the lamp and it should also work properly if you plugged it directly into the outlet without dimmer. If these assumptions are correct, then it is the combination of dimmer and LED that may be the issues. Some LEDs are very picky about dimmers, it is a little bit of trial and error.

Good luck.
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Re: Coincidence, or not? LED; Theory or Conspiracy?
Posted by: max
Date: April 15, 2019 09:05PM
Try out your lamp with a cheap LED bulb, the dumber the better, it might work out a lot better....
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Re: Coincidence, or not? LED; Theory or Conspiracy?
Posted by: mrlynn
Date: April 16, 2019 09:48PM
Incandescent bulbs work fine with dimmers. Write your Congressman: bring 'em back!

/Mr Lynn
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Re: Coincidence, or not? LED; Theory or Conspiracy?
Posted by: Winston
Date: April 16, 2019 10:23PM
As the lamp and bulb socket is simply a way to connect wiring to the bulb, the bulb socket seems like the only thing which could have changed that would affect the bulb. (I assume by "rebuilt" you mean you replaced the lamp socket.)

I'm not an expert on this, but is there a chance that the rebuilt lamp's socket has neutral and hot reversed, and that LED bulbs are sensitive to this?

We have an enclosed hanging fixture which uses a 150 W candelabra base halogen bulb. At some point the socket had a problem, so I replaced the socket with a 150 W rated one. The lamp started eating bulbs. Solution was to get a 300 W rated socket, and all has been good since. The 300 W socket is all porcelain, whereas the 150W one was mostly plastic. I'm guessing that somehow the replacement 150 W socket allowed the bulbs to get even hotter than halogens get already, causing the premature failures.

Could the replacement socket have a different shape and be blocking cooling airflow to the base of the LED bulb? I know many LED bulbs have cooling fins.

Good luck.

- Winston

Be seeing you.
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