Re: adding earth lead to vintage radio
In those circumstances, adding the Y2 capacitor would nullify any safety advantage from earthing the chassis, though it would leave any RF improvement intact. The point of a safety earth to the chassis is simply to prevent the chassis from becoming live in the event of an insulation failure in the mains transformer (or possibly a stray broken off live wire coming into contact with the chassis). It does this effectively (historically) by blowing the supply fuse in the event of such a failure or more likely nowadays by tripping any RCD in the supply.
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