I was changing several LED bulbs in recessed fixtures in
the kitchen ceiling. One bulb, non-functional for months,
was warm to the touch. If I put this same bulb in another
socket with the current on, it will not light but within
fifteen minutes it will be warm to the touch again, although
not as warm as it was in the recessed fixture. The other
LED bulbs I replaced (different brands) were not warm
to the touch and do not warm up when energized.

I asked about this at the hardware store where I got
replacement bulbs. They were unfamiliar with this
characteristic, although they did say that LED bulbs
should not be used in an enclosed fixture unless they
are rated for that application.

I am interested in any information about this phenomenon.

Thank you in advance for any replies.

Peter Wezeman
anti-social Darwinist

In article <79cca283-6be9-4ae2-bc75-59b6c6840a12n@googlegroups.com>,
peterwezeman@hotmail.com <peterwezeman@hotmail.com> wrote:
>I was changing several LED bulbs in recessed fixtures in
>the kitchen ceiling. One bulb, non-functional for months,
>was warm to the touch. If I put this same bulb in another
>socket with the current on, it will not light but within
>fifteen minutes it will be warm to the touch again, although
>not as warm as it was in the recessed fixture. The other
>LED bulbs I replaced (different brands) were not warm
>to the touch and do not warm up when energized.
>
>I asked about this at the hardware store where I got
>replacement bulbs. They were unfamiliar with this
>characteristic, although they did say that LED bulbs
>should not be used in an enclosed fixture unless they
>are rated for that application.
>
>I am interested in any information about this phenomenon.
>
>Thank you in advance for any replies.

(Hal Heydt)
An LED is a forward biased PN junction diode. It runs on low
voltage (~3-8v or thereabouts) DC. Your light socket provides
(depending on country) 110-240v AC. So there is voltage
conversion and rectification required and that circuitry could
still be actively running even if the LED(s) them/itself has
failed.

(I was, back when rocks were soft, an EECS major. I'm a lousy
EE, but it made me a pretty good programmer. Some of the EE
stuck, though.)

On 24.09.22 0:50, peterwezeman@hotmail.com wrote:
> I was changing several LED bulbs in recessed fixtures in
> the kitchen ceiling. One bulb, non-functional for months,
> was warm to the touch. If I put this same bulb in another
> socket with the current on, it will not light but within
> fifteen minutes it will be warm to the touch again, although
> not as warm as it was in the recessed fixture. The other
> LED bulbs I replaced (different brands) were not warm
> to the touch and do not warm up when energized.
>
> I asked about this at the hardware store where I got
> replacement bulbs. They were unfamiliar with this
> characteristic, although they did say that LED bulbs
> should not be used in an enclosed fixture unless they
> are rated for that application.
>
> I am interested in any information about this phenomenon.
>
> Thank you in advance for any replies.
>
> Peter Wezeman
> anti-social Darwinist
>
For silicon I learned that each 6 dgr Celsius halved the
survival time.
Similar figures can be expected for LED lights.
So yes, they survive much longer in cool air.
That goes for all semiconductors,