This is a very common problem with denon receivers of the 2001-2-3 vintage. On almost every one, there are 4 little "surge" resistors in the power supply. These werent quite robust enough from the factory and one day would just burn open for no reason. Well, actually there is a reason, the "surge" that happens every time you power the unit up eventually weakens the resistors and then they pop.
You need to take this to a denon service shop as I GUARANTEE they have seen this before. They need to check resistors in the picture, locarde above the **** rectangular connector. Resistors numbers R141, 142, 148, 149:
These resistors when measured, should be less than 10 ohms each. If they are more, then they are blown. If they are blown, then have the shop check the channels for blown output transistors. If the outputs are OK, then these resistors should be replaced with 1 ohm 1/2 watt metal -film flameproof resistors.
You might need to be prepared for a large bill, because the entire unit must come apart to replace the resistors, however, just checking them takes only about 10 minutes...
Good luck and don't try this at home.