The way these avr's work is like this. They have two power supplies.
One is the massive one which uses the transformer. This is the inefficient power supply, but this is the workhorse. This powers all the amps inside your avr. Keeping this on always even when not playing music will waste electricity. So to avoid this and to adhere to Euro norms, manufacturers came up with the idea of a second power supply that is efficient and can switch on the main supply at the click of a button.
So we have a second power supply - an efficient SMPS which powers all your digital boards. Since SMPS are efficient this is used as as the standby power supply which powers the remote control circuit that gets operated through your remote. In standby mode your AVR will consume very very little power because the main transformer based supply is off. When you press the power button on remote or on the front unit, this standby supply switches on the relay to turn on the transformer based supply. SMPS based supplies are not as rugged as the heavy duty transformer based supply as there are so many components that go into building the SMPS. In contrast the heavy duty transformer based supply has the transformer, diodes for rectification and few capacitor to act as reservoirs of electric charge.
IME experince most SMPS give away mostly because of the controller IC or a small capacitor. You can do a visual examination of components on this board. This is the board to which the power supply cable connects to. This will the board just in front of the power supply cable. Also in most cases I see this board fitted vertically inside the chasis, while all other boards are placed horizontally.
If your standby led is not turning on it means the cheap SMPS supply is not powering on. Mostly likely it is the IC. It is usually some TOP254, TOP258, etc in Yamaha, Denon and Marantz. Cost of the IC is less han 100 bucks. If you give it to authorized service center, they will replace the entire board which will cost north of Rs 20k
