>a) charging through the 10K resistor toward 24V potential >until it hits 16V, at which time it's limited by the zener? Below 16V the zener does not draw any current, so you can pretend it is not in the circuit (ideal zener, anyway). Above 16V the zener will draw the current, not the cap. Barry -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics