Sony TA-1630 baffling me
Suggest you replace the output stage emitter resistors with 100 Ohm or higher for the purposes of testing.  This will at least allow you to power it up without the O/P failing before you can even make voltage measurements.  Suspect the bias pot, in many circuits if the bias pot opens up or the wiper goes high resistance the bias into the O/P devices goes to the maximum the circuit can support.  O/P device failure is near instantaneous if that's the case.