It doesn't replace the optocoupler. I would rather have the opto, however, after a recent string of failures, I am trying to minimize my repairs and use something more reliable like resistors.

So, if I use the Zener to regulate down to 5 volts, would I use a VD setup that brings the voltage down to say around 6 or 7 volts and regulate from there, or just use a single resistor for the load on the Zener?

My understanding is that the Zener should not be the only thing regulating the supply because it will blow. It WILL need to go through a resistor. Does this sound right?

Thanks,
Tony