This unit sold from 2012-2015 as the top-of-the line AV Network Receiver from Denon. I got my hands on a unit with power protection issues. Here's the repair log the Denon AVR-4520.
A classic 1989 Denon PMA 720a Integrated Amp that made a bang and wont't turn on. Let's solve this!
Log of diagnosing and repairing a Denon PMA560 Stereo integrated amplifier.