ok, the first thing i do when i have one of these on the bench is to find out which channel is blown. the collectors of all the output devices are tied to the positive or negative rail. this means you can quickly find the shorted output devices by clipping one lead of an ohmmeter in diode check (my meter has a beeper for shorts in that mode) to a collector (Denon receivers use 2SB/2SD pairs) of one of the output devices and going down the rows of transistors with the other lead and looking for shorts between any emitter pins and the rail you're on. if you're clipped to an NPN collector (D2390 center pin) , you're checking from the positive rail, if you're clipped to a PNP (B1560 center pin), you're checking from the negative rail. the pinout of all of these transistors is BCE, so all of the third pins are emitters. so, you connect one lead to any center pin of a D2390, and use the other lead to check continuity to all of the D2390 emitters, then clip to the center pin of a B1560 and use the meter to check continuity to all of the B1560 emitters. you will most likely find a pair of D2390/B1560 transistors shorted, this is the blown channel. on occasion all that's blown are the two transistors and their emitter resistors (should be (4) 0.22 ohm/ 1/2 watt resistors). unfortunately with Denon amps, the damage may go back further. there's a string of bias limiting diodes (2 zeners and 2 regular diodes) and the bias transistor. then there is the "preamp" board or section which consists of a differential pair and a voltage amplifier. there's rarely a problem with these, but i have seen it happen... you will want to check any flameproof resistors in the blown channel since they can burn open with little or no visual indication that they burned.
also be aware that there's a protection trigger transistor and sometimes this shorts as well, so you could get the amp itself repaired correctly and still get an error condition.
also be aware Denon receivers can be built like a 3D puzzle, and difficult to troubleshoot if not taken apart. and very difficult to get back together if you don't pay close attention to where all of the PC boards and cables plug in. there is an "en-bloc" (one piece) way of getting it apart, but that takes a bit of experience to do...