I pull the transistor and check it before trying anything else. If the transistor works, write down some of the curve tracer measurements. You may accidentally fry it during repair. You will want a transistor that can stand off at least 1.5X the peak primary DC voltage, preferably 2X. You will need to find what the current rating of the transistor you pulled out is, and meet that with the replacement. Same or lower capacitance Advances in components make finding an adequate replacement possible.
Curve trace the replacement.
The result of a diode failure is usually an imbalance in secondary voltages. Regulator ICs - these rarely fail, but a manufacturer can get a bad batch. The result is a whole bunch of the same supply type failing. The ticking noise means the regulation loop is broken somewhere. You may have a heck of a time finding a replacement.