I think I’ve found the issue. EDID.
The EDID or Extended Display Identification Data is a packet of information sent from a monitor or TV to the source of the video and tells the source what types of video the display can process.
Imagine for a moment that we have a receiver from 2013 – pre 4K – that contains an HDMI switch. Now imagine that one buys almost any TV today – almost all of them support 4K. Now imagine that one purchases something that produces video – BluRay player, XBox Console, Playstation, even a modern set top box. Most of these support 4K video.
So what happens if the EDID from the 4K TV passes unchanged through the NR1504 from 2013 to the video source that can produce 4K? Well the source happily produces 4K video and the NR1504 cannot pass it. Black screen? Apparently.
Was the Marantz 1504 never modifying the EDID? Or did it just start not modifying the EDID? Or did the Linux computer get a new driver that was willing to produce 4K video?
I hooked up an HD monitor to the NR1504 and hooked the Linux box back up to the Media input and voila. Everything works fine, of course.
It seems clear that in this world of ubiquitous 4K sources and displays, the Marantz NR1504 needs to be modifying the EDID or producing one of it’s own to continue to work.
I’ve used the display settings in Linux to use HD only and that works fine with the TV, but when I plugged it back into the NR1504 it still didn’t work. Oh well. Time for a new Receiver that gets 4K. But at least I can use the Linux system by plugging it directly into the TV and setting it to HD.