[Phlogiston]

Keep in mind that the proper size fuse can still blow, which is probably why few of the old radios are fused. One of the most common ways to blow the "proper" fuse is to turn a warm radio off then immediately turn it back on - how do I know? Little hands at a radio show

His dad said "he likes to play with knobs". Great! Maybe you should buy him a radio to play with (rather than playing with mine).