Yamaha RX-V663 zone 2 stopped working.... I no longer hear the 'relay clicking sound' when activating zone 2...how do I fix this?

Hello
The power supply sectionand the relay control section should be checked. There is control transistors which activates the relay control. If this transistor has damaged, of it does not get any voltage, the relay will not click. In most cases, if the output transistors got shorted, the set will come by protection state. Here you reports that only relay is not working. Just open the set and check the voltages at the "collector" pin of the relay drive transistor. You have ot disassemble the whole circuit board as these transistors are not accessable without get the boads out. Actuallly this is a very skilled work and care should be taken in all respect. If you are not aware in elctronics, and haven't proper tools and a digital multimeter, soldering iron, you can do this work. Otherwise get it repaired by any experienced service technician. OK.