How can I tell a LED is blown out?

[Paul Hovnanian P.E.]

Is there a visual way of sussing whether a LED is blown out? Testing
it with a battery confirms it is blown out, but I wondered if there is
a visual way of seeing the actual burnt out parts...

Not necessarily. Some failures might not be evident by a simple visual
examination.

If it stops putting out light and/or it is no longer operating within
specification electrically, its 'blown out'.

 

[StickThatInYourPipeAndSmokeIt]

Not necessarily. Some failures might not be evident by a simple visual
examination.

If it stops putting out light and/or it is no longer operating within
specification electrically, its 'blown out'.

Yep. Even if it continues to act as a diode, if it is not putting out
human visible spectrum photons in an appreciable quantity, it cannot be a
Light Emitting Diode.

We are, of course,talking about standard LEDs.

So much for common sense.