can you fill us in on what test equipment you have? I would start by measuring voltages on the RX tags listed in th3 schematic. I would then try supplying a signal to the audio section (sometime the hum from touching th3 test point is enough).
If I am reading your comments correctly, I think you may have a short somewhere in the RX power supply. ESP if all of the audio sections are down. That was wh6 testing the voltages first, the going to audio signal injection to see where the signal is lost.
Good luck, and happy hunting:)