Scopes made out of modified TV boxes are slower because TV CRTs use magnetic deflection (through those big coils on its back) which is slower compared to electr

Scopes made out of modified TV boxes are slower because TV CRTs use magnetic deflection (through those big coils on its back) which is slower compared to electrostatic deflection used in "real" scopes CRTs. That is, even adding high quality input circuitry, the frequencies used and TV CRTs nature won't allow much beyond audio frequencies. That shouldn't discourage experimenters though, as even a 5 bucks ex flea market portable b/w CRT mini TV could still make for example a really nifty curve tracer once paired to a cheap MCU generating the necessary signals.