first test on a differemt deck. if they play ok, chances are the pinch roller in the aiwa needs cleaning or replacing.
if still sluggish the tape binder has broken down, this is tricky as ampex used whale oil between approx 1975-1983 in the manufactuing process, which has not aged well. you may have to 'bake it' - google tape baking.-
good luck.
romko
February 2007