[sci.electronics] Glowing diode

brand@csgrad.cs.vt.edu (01/23/91)

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...