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UV LEDs die fast?

Out of a batch of 50 UV LEDs two have "died" somehow. With the first one I thought it was a bad connection, so I re-soldered the LED, and it worked. When I turned the circuit off for some time, same problem. So again I thought: "cold" connection, re-heated it, and worked...

But when the circuit got cold again, same problem. I replaced the LED, and no problems for hours.

Two days ago, however, another LED stopped working, same problem. Heating it, it works again. This time I was able to "see" (indirectly, UV LEDs can harm your eyes) what happened: the three LEDs in series started to flicker for some time, and then all went off. Heating it -> works.

Does anyone have an idea why this is happening? Just 2 bad LEDs out of 50?

See

formatting link
for the circuit diagram.

Also: I use most of the time 9V to feed this circuit, so I doubt it has anything to do with overloading the LEDs.

TIA,

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John                               MexIT: http://johnbokma.com/mexit/
                           personal page:       http://johnbokma.com/
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Reply to
John Bokma
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John Bokma explained :

look at the traces leading to the led. Is a pad lifted? or has a crack in the board developed?. reheating is the key common factor.. I'd look for external faults before the led.

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Reply to
Lawrence Oravetz

2 more leds have died. I bought a digital meter, and am going to do some measurement. I got more and more the impression that the shop sold me garbage. (Especially since I use 9V to run the circuit, not 12). 
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John                               MexIT: http://johnbokma.com/mexit/
                           personal page:       http://johnbokma.com/
        Experienced programmer available:     http://castleamber.com/
            Happy Customers: http://castleamber.com/testimonials.html
Reply to
John Bokma

Should you determine that it is the LEDs, could you tell us what brand these LEDs are?

- Don Klipstein ( snipped-for-privacy@misty.com)

Reply to
Don Klipstein

I have no idea about the brand, but I ordered them from LSDiodes.com. They seem to have a good reputation, but I am amazed that I manged to kill 4 UV LEDs, especially since I thought they would last for thousands of hours.

I'll check it out next week.

--
John                               MexIT: http://johnbokma.com/mexit/
                           personal page:       http://johnbokma.com/
        Experienced programmer available:     http://castleamber.com/
            Happy Customers: http://castleamber.com/testimonials.html
Reply to
John Bokma

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