Do you have the trouble shooting manual? In section 5.6 is says "check for audio signal at the base of Q301. Is the audio signal received?" If not check audio input circuit Q301, C301, R301, and input cable.
If you have audio signal, go and check for signal at the collector of Q302. Is the audio signal received? If not check Q302, Q304, Q301, R315, C302, C306, R305, and R317.
If yes check audio output circuit. Q303, Q304, R318, R316, C305, C310, D301, T301, Output cable, and speaker.
I just checked my transformer, the black and white side had about 30 ohms and the red / white side had around 2 ohms. Mine has never been used, since the machine it came from had its own amp.