I’ve got two different devices that output HDMI at 1080P.
Monitor #1 works with both device #1 and device #2.
Monitor #2 only works with device #2.
I preempt anyone with this xkcd, but still. If monitor #1 can understand the signal from both and monitor #2 can understand the signal from device #2 then why not from device #1.
This is a bit of a long shot, but you might want to make sure that your monitor #2 is capable of 1080p. In theory, a device trying to drive a monitor that can’t do 1080p should step down to a lower resolution, but I recently encountered a Windows PC that kept trying to output 1080p video to a monitor that maxed out at 1440x900. Result: blank screen.
Some devices (e.g. your device #2) might be less stubborn and accommodate a lower resolution by switching its output resolution itself automatically. Of course, if you can tell that monitor #2 is working at full resolution with device #2, that’s not the issue.
Like I said, I saw this just a couple weeks ago, so it may be worth your while to check. Good luck!
What are the devices? It may be that monitor #2 is compatible with HDCP (encryption over HDMI), and the other not, while device #2 only outputs HDCP signals (say, if it’s a Blu-Ray player), and device #1 does not require it (a computer, say).
I guess it is complicated. Device #1 is a ten year old win10 PC and device #2 is a 10 year old Roku XS. Monitor #1 is a Dell D3218 and monitor #2 is a Sony Bravia KDL40WL. From what I can tell none of them do HDCP.
It’s tough to find any manuals or spec sheets for devices that old, but I’d definitely suspect HDCP. HDCP was mandated by content producers, so it appeared first in TV-adjacent devices. So, the Roku (probably) only outputs HDCP, and only the TV consumes it. The PC doesn’t care one way or another.
That’s probably it. The video card in the PC doesn’t mention supporting HDCP and the Sony TVs starting doing that in 2013. Life used to be so simple with VGA/CGA/EGA.
This is what I find odd. I tried rebooting the PC while connected to the sony and you could see it booting… then red screen… reboot. Why does the PC even know or care WHAT is connected to the HDMI cable.
Just to be sure, swap the HDMI cables on your devices. Maybe the other starts failing.