http://www.geocities.com/gpg212/scirepair2.GIF
When the control transistor is turned on it biases the gate of the FET
on. The zener limits the gate voltage

thanks for the schematic. Now I know that the zener limits the gate
voltage. But I still can't find out the reason why is there no drain
voltage present. Is there a possibility of a defective MOSFET ? Low
voltage power supply seems ok. The zener and resistor are ok too when
tested by ohmmeter.

ian