[Studio263]

If the transistor gets hot it is because it isn't being turned fully on, or is being turned off too slowly. I would try something like a MJE340 and reduce the value of R514 from 3.3R to perhaps 1 or 1.5R and see if it runs cool. Sony's own transistors have higher current gain (hfe) than normal ones which is why increasing the base drive often helps. Also check C520, which will distort the line drive waveform if it is 'tired'.

This is a low voltage / high current line output stage - the line pulses on the transistor's collector are only 175V. Darlington transistors are not suitable here as they are too slow.