https://www.reddit.com/r/typewriters/comments/1mlck21/early_60s_selectric_i_doesnt_turn_on_thoughts/

Working on this Selectric I picked up. I was wrong on the date, it's a 1970 based on the serial number, and I think it just needs a good cleaning and lube, since it now powers on and the motor spins up, but it's really just...sticky. It was serviced last in 1984, according to the little record sheet I found tucked behind the lever to release the cover, so 40 year old congealed oil is probably the only thing really "wrong" with it.