Denon AVR-X 4700H suddenly stopped working

[reamai]

We just came back from a one month holiday and when we turned on our Denon receiver it worked fine for the first 5 minutes. Suddenly, the calibration screen appeared and all the speakers started making a non-stop popping noise (one pop every 0.5 second sounds a bit like a fast heartbeat) .

I've tried resetting settings and restoring firmware following this procedure here https://manuals.denon.com/avrx4700h/na/en/RQIFSYfmmhttob.php
After reseting, when the menu shows up, no sound come out of the speaker until we get to the calibration screen. When it asks if we hear the noise from the front left speaker, all speakers make that popping noise (but the left front speaker is slightly louder). Same for all steps in calibration.

When playing music through heos (using spotify), we can only hear the popping sound.

When I plug in the headphones, the speakers stop making that popping noise, but I hear that noise through the headphones.

What are the next steps? Given that it's out of warranty, is it better to try and get some off-label repair service? Anyone knows a good place in HK or Shenzhen?

Rather disappointed, it's only 5 years old.

EDIT: I turned on the AVR after having turned it off for 10 minutes to see if it would work if I used the pre-out instead. When I turned it on, sound worked again. But a few minutes it did the same thing, switched to the audio calibration screen and started doing that heartbeat sound.

 

[kiwifi]

Try the following... Disconnect the power cable. Take the top cover off and blow out any dust with compressed air.

 

[Chrispy]

I'd have tried the factory/microprocessor reset first.....have you tried that at all?

 

[reamai]

I'd have tried the factory/microprocessor reset first.....have you tried that at all?

Thanks, I've just done that using this process https://manuals.denon.com/AVRX4700H/NA/EN/GFNFSYvyalrwrt.php and so far so good, it's been working for an hour.

I did originally do "Reset All Settings" from the menu which I thought was the same as that procedure but that didn't help. So I'm not sure if it's working because I reseted the settings or because there's a bad contact somewhere or something else that could cause this (weather has been 90+% humidity in the past few days)

 

[Chrispy]

Generally I'd just use a soft reset when something glitches, they're like buggy computers (soft reset is just unplugging it from power for a bit). You did a network reset first rather than a general factory/microprocessor reset, which may resolve a network issue....

Thanks, I've just done that using this process https://manuals.denon.com/AVRX4700H/NA/EN/GFNFSYvyalrwrt.php and so far so good, it's been working for an hour.

I did originally do "Reset All Settings" from the menu which I thought was the same as that procedure but that didn't help. So I'm not sure if it's working because I reseted the settings or because there's a bad contact somewhere or something else that could cause this (weather has been 90+% humidity in the past few days)