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From: brand@csgrad.cs.vt.edu
Newsgroups: sci.electronics
Subject: Glowing diode (was Re: LED history)
Summary: Almost anything can be light emitting
Message-ID: <854@creatures.cs.vt.edu>
Date: 23 Jan 91 03:38:33 GMT
References: <1991Jan16.034246.12843@zoo.toronto.edu> <1962@atlas.tegra.COM>
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Reply-To: brand@csgrad.cs.vt.edu ()
Organization: Virginia Tech Computer Science, Blacksburg, VA
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In article <1962@atlas.tegra.COM> vail@tegra.COM (Johnathan Vail) writes:
>
>[...] I was working on a CD player and on the circuit
>board was a normal looking glass diode, cathode band and all, that lit
>up red.  It wasn't an indicator, and had a normal D number like the
>other real diodes on the board.
>
>Was the light emitted a side effect of the diode?

I've seen this happen *once* with a normal signal diode (1N1418).  I too was
quite surprised, and I was disappointed when it went out after a bit.  I soon
found that it had been carrying a short across a 6V lantern battery.  Suddenly
the red-orange light wasn't nearly so puzzling.

This can also be done with transistors, EEPROMS, Mylar-coated balloons...

Seriously, this *could* be a valuable diagnostic; if the problem with the CD
player produces a short-circuit through that diode, well, there you go.  Oh,
and don't forget to replace the diode after you fix the main problem; annealing
isn't good for junctions.

	-jeffB (Jeff Brandenburg, Va. Tech CS)
	Master of 20W light-emitting small components

	brand@vtcc1.cc.vt.edu     Meet the new age / same as the old age...