>>
>> Have you considered using a capacitive reactance instead of a resistor to
drop
>> line voltage?  I think I remember an RCA temperature controller chip, CA30??
>> maybe, that worked this way.  You can use a capacitive divider or a capacitor
>> sourcing current across a resistor to get low voltage AC and then rectify and
>> filter it after the divider.
>>
>>
>Yes, capacitive reactance is a more elegant solution from a conceptual
>standpoint. But you need a voltage rating equal to the max peak line
>voltage plus safety factor. The capacitance needed for practical values
>of output current, combined with the required voltage rating, result in
>a capacitor that's physically pretty large. A lot larger than the
>power resistor it would replace. But if you have plenty of space and are
>more worried about heat, it could be a good design approach.
>

When using a capacitor, be sure to include a small (10-100 ohms) resistor in
series with it.  Since voltage spikes (by definition) have fast risetimes,
they will couple straight through the capacitor with little attenuation and
possibly damage the rectifier diodes or other parts of the regulator.  The
capacitor, being large, will not experience a voltage transient, but a heavy
current transient will couple through it.  The protection resistor and other
resistances in the circuit are the only limiting factor.   Special resistors
intended to function as fuses are available that can combine the fuse and
resistor functions in one part.  Lacking those, a conventional "flameproof"
resistor would be suitable for ordinary hacker use.

-Mike