110v/220v switch is
underneath, inside. Turn it upside down, get a torch, and have a look.
Also here's a pic of the underside (yeah, I've messed with the brightness/contrast for clarity). 110v/220v switch is dead centre.
The broken knob is the stereo/mono switch, next to the headphone jack. Left is stereo.
The dial above the two controller ports is to adjust the overall brightness.
Right of the power is a +/-5 screw to be used with the provided screwdriver.
Top middle adjusts sharpness.