HealthKit mr11 power connection

I inherited a Heathkit MR11 directional receiver. There are two ports, a speaker, and a power port, there are no cables included. So I have determined the speaker port because it is wired in parallel to an internal speaker. The power port is for 9 volt I have determined from other schematics, the concern is polarity, tip is +, ring is - , at least I assume that? The wires going to the power port are both blue coated, no other markings and very thin, 20 to 22 gauge. So can anyone give some insight prior to me connecting the 9 v battery…. Please, mom always said say please!  pgdoug@gmail.com