If that Betamax works, I'm interested in it. Long story.
Confirm it works if there are any of your dad's tapes around, then PM me a price + shipping, and I'll send you a Wells Fargo money order pronto.
When you put a tape in, rewind it to the beginning, then fast forward it to the end, then rewind it to the beginning again before attempting to play it. Supposedly, that limbers up a sketchy or semi-sketchy tape.