Those 75 ohm coaxial cables from and to the receiver will have to be replace by audio cables. Also I noted in your question that the TT is connected to the Receiver's Tape-In also you have the Computer Line Out ALSO connected to the Receiver's Tape-In, unless you have 2 tape monitor circuits this will not work. Connect the TT to some other Line input such as AUX. Set the source to that input and turn on the tape monitor to hear what is be recorded from the computer.
Hope this helps
Regards,
Rich
Hope this helps
Regards,
Rich