Yeah i had the exact machine back in the 80s... You have to slide that lever in front to unloop the tape, then push it down and the door pops up, Same to load: Insert tape, push down door, slide the lever to the right to load tape, press play... Its a cool machine...
On the back or side there should be a panel that holds a modulator of some sort, open door, grasp handle and the module pops out...Interesting unit... and HEAVY...
SR