[amptramp]

If you have a 120 VAC line and you have two equal capacitors from line to chassis, the chassis will remain at 60 VAC because you have a voltage divider between the neutral and hot side and the neutral is grounded.  If you have a three-prong plug with the ground connected, the chassis will be at ground potential.  The capacitors are there to avoid noise conducted from the AC line getting into the circuitry and to avoid emission of noise (especially oscillator noise for the superheterodyne sets).