No audio output

If you already change the STK still not working,next step you do is to checked the resistor; the transistor ;capacitor(electrolytic only) and the diodes only in the power Amp section,where you change the STK,checked them out that they are, connected to the pins of the STK, one cut out or breaks can cause no audio out,,most sign of spare busted is the resistor is going to change the value of the resistance or open ; the capacitor is shorted ;open or leak;the diodes shorted or open ;transistor shorted or open;;that are common defects,you better look first the resistor ,there is limiting resistor to limit the source maybe that is the problem also,try this option this very of that problem of yours ;if ever my answer help to uderstand the problem please rate me as a fixya...

Try this check the connection firts because that's one of the most common thing to check, then check the adapter switch left on (either on front or rear panel) and checj for missing jumpers on the back.... pre-amp out to main amp in, if still the same problem it will goes down it replacing a piece of sound amplifier inside it just liek what happen with mine.
Hope that helps...........

Check the last output stage before the speaker output. A blown diode may have caused back emf to blow the power transistor.

Hmmm...did you check the speakers to ensure that there is no short?

Check whether the plugs are inserted properly and check whether the pins are working properly