OK I did a bench test. But, no way I'm going to do the 120VAC/resistor/LED trick.
Normal forward bias connection of a red LED with a current-limited power supply: Vf=1.9v@If=20mA
Reverse Connection: Ir=~0 mA @ Vr <24V. As Vr was increased above 25V, Ir rapidly increased to 30mA. The LED was getting hot!
A combination of the 10K resistor limiting the reverse current to 12mA (120v/10K) would keep the LED from going Poof. But this cannot be doing the LED any good in the long run. A single diode, connect with opposite polarity across the LED would make the LED operate within its specified limits.
be80be,
Do you have any examples of this configuration used in commercial, or hobby, devices?
Ken