You gotta give it a few slaps too, when the image isn't very clear.

Pre-Gameboy, when I was a child, my grandfather had a television— the kind that was furniture. Sometimes it would eschew modern trappings like colour and v-sync, and I would employ my Classical Vaudevillian training to set it straight with a wallop.

I always had to rap my knuckle on the screen. It has that nice, thick hollow resonance

Good ol' percussive maintenance.