Steve,

We use alot of PTH LEDs, as far as I know , I dont believe we have seen this
problem with PTH, we have with SMT LEDs, diffuser breaking off due to
incorrect heat and handling problems.

This might seem like a dumb question but are the replaced LEDs passing test
or failing after extended power on times?

How do the failed LEDs test with DMM out of Circuit?

Can you perform a functional test on removed LED with 1K resistor and 5vdc
source, this will put  5ma of current, (should not damage
LEDs, its less than 25ma) to see if they emit light?

I'm wondering if it is EOS (electrical over-stress) too much current, design
flaw or wrong component may be damaging them?

If not "test kills" then forgrt my ramblings!


Tom Braswell

-----Original Message-----
From: Stephen R. Gregory <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, December 29, 1998 3:06 PM
Subject: Re: [TN] Assy: LED Failures...


>In a message dated 12/29/98 11:29:21 AM Pacific Standard Time, [log in to unmask]
>writes:
>
><< Are your LED's surface mount or through hole?
>  >>
>
>Hi Mark!
>
>     Yeah, 'bout your plant shutting down over the holidays, same here too.
We
>were SUPPOSED to be shut down too, but a customer brought this kit of
>transceivers over along with another job that they just HAD TO HAVE back
>before the first of the year... you know how that goes. I guess there's one
>thing good about working now, don't have to deal with the gridlock we have
>here in "Silicon Valley" going to and from work 'cause everybody else is
>off...just gotta' be able to see through the fog (it's literally been as
thick
>as pea soup out here the last few days)
>
>    Where were we? Oh LED's...the ones I'm dealing with are PTH, little
radial
>square buggers, about .250" square. They go on a .040" stand-off too. I'm
>using the same kind of parameters that I wave most of my boards with, you
>know, nothing unusual. This board does have surface mount on the bottom so
I'm
>using a chip-wave too. I've waved other boards with PTH LED's before and
not
>had as many dead ones as I'm getting now...
>
>-Steve Gregory-
>
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