I think it was in the late 70s/early 80s an anime movie appeared on HBO. During that time HBO mailed a monthly TV Guide of prominent movies being aired and I think it had a high profile spot.
I don't think the name of the movie is Space Dragon because I rented that already and it seemed different from what I remember.
I remember the main character tries to assemble the robot but is unable to and gets injured in the process. It's kind of like the Voltron robot but with just one person controlling the robot.