Could old TV broadcasts reach alien civilizations?

Yes, in principle — old TV and radio broadcasts have been expanding outward from Earth at the speed of light, so a civilization within roughly the broadcast’s age in light-years could have those signals passing by now.

For example, broadcasts from the 1930s–1950s would now be tens to nearly a hundred light-years away. So any star system within that radius is in the “signal bubble.”

But in practice, it would be very hard for aliens to detect normal TV broadcasts. Broadcast TV signals spread out and become extremely weak with distance, and much of the energy was aimed toward the horizon rather than deliberately beamed into space. A very advanced civilization with huge receiving equipment might detect some leakage, but decoding a watchable episode of old TV from many light-years away would be far more difficult.

The more detectable human signals are powerful, narrow, directed transmissions — like radar pulses — not ordinary entertainment broadcasts.