How to obtain a little 120 VDC from 240 VAC?
Here's a simple way to get regulated 120 volts, DC from 240 volt mains, but DANGER, WILL ROBINSON!!! it's not isolated from the mains, so if you get 240 hot and 240 neutral connected backwards it could seriously fry some equipment or make you dead.

If you want to play with the circuit, here's the LTspice .asc file you can use to run a simulation.