On Friday, February 6, 2015 at 3:01:05 PM UTC-8, Scotophor wrote:
On Friday, February 6, 2015 at 8:45:48 AM UTC-8, wrote:
On Monday, February 2, 2015 at 3:17:21 PM UTC-8, Scotophor wrote:
I'm seeking some out-of-production discrete through-hole component LED light bars for a project. There are two different styles that I want and can not substitute. According to a couple of archived internet postings, they were reportedly manufacturer-discontinued in either the late 1970s or early 1990s, but remained somewhat available until around 2000 because at least two distributors had bought the manufacturers' remaining stocks as surplus and sold them in retail packaging.


Consider the possibility that they were discontinued because they were
not very satisfactory. That is a LOT of epoxy in there. Stress from
the encapsulant on the die, exacerbated by the heating of the die
from the power dissipation, will promote the growth of defects, which
raises the dark current, which accelerates the wearout of the die.

More concisely, you wouldn't want to locate a cache of these ancient
parts, only to have to go through them like Kleenex.

The discussion on the other forum, where the fellow will overmold
conventionally encapsulated LEDs in the desired form factor for you,
sounds far more promising.

I fail to understand how dark current is applicable here.

Dark current is (leakage) current that does not contribute to light
output. It increases as the various crystal defects grow and propagate.
LED failure is generally defined as the point where the light output
has dropped by 50%. Selection of encapsulant can either accelerate or
retard this effect.

Statistically speaking, I find it hard to believe that: upon identifying the LEDs, (A) I already had two of them, unused, among my supplies, (B) I already knew someone whom I believed might also have some, which I was able to verify in minutes by browsing his website. I later obtained more than a dozen of them from him, a mix of unused examples and pulls. (C) Within days I had found another person online who sent me three more, yet (D) In the 6+ months since, I have not been able to locate even a single additional example. What are the odds that I could locate and acquire the world's entire available supply of these in such a short time, and that I already knew the person who had most of them? It boggles my mind to think that I found as many as I did so quickly, yet there now don't appear to be any more to be had, anywhere. I believe there must be more out there; it's just going to take more time and effort to discover them.

Sooner or later, crap tends to get flushed.