hifi engine

Nikko TRM 40LA

Hello, Iam looking for a schematic/curcuit diagram for a Nikko TRM 40 LA. It has been in my possesion since 'around 1970 and was bought new for me by my Dad. It still works, but only the right channel. I would love to get it working again, but dont really stand a chance without a diagram.
Can any body help?

Cheers Julian robinson