Nakamichi CR-1: Service Manual/ plan needed
 

I need a circuit diagram for a Tape Deck
(Cassette Recorder)Nakamichi CR-1.
At playback, the positive amplitudes one channel
is too flat (sorry for my english).
There are 2 transistors near the cinch-connectors,
does anyone know their function? Both are connected
to the same "wire" at the board, so for me this makes no sense.

Stefan