Hi,
Welcome to the Forum.
I'll assume you have your speaker wires connected correctly, and you can get sound with the Tuner, or another input.
Let's start with when you put in a Cassette with music on it do the meters light up during play like on this YouTube?
Sanyo DCX-1970K Playing
If so you may have reversed the connections on the back that go to the Sanyo DCX 1970K receiver, or possibly need to press Tape Monitor button on the Front Panel of the Receiver (bottom right in the photo below),and slowly turn up the volume from zero.