check fuses , make sure your problem doesn't stem from operator error (wrong input , tape monitor , wrong connection , a or b speakers switches, etc.) .there are many ways to not get sound from a working amplifier , otherwise look for a repair shop that does this sort of repair as the parts are sometimes difficult to find , you need specialized test equipment sometimes and schematics . and don't be surprised if the repair cost is high.
but i did have a toshiba amplifier at one time and i was very pleased with it , i believe it was of a 80's vintage .
ps , if you are particular to this model of receiver , there is one for sale on craigslist Minneapolis MN asking $50 http://minneapolis.craigslist.org/hnp/ele/2650013323.html