Help requested with Yamaha RX-A760 video issue (1 Viewer)

[Tuthmose]

Greetings,

I’ve got a conundrum I’m hoping somebody can help with.

I built an A/V setup in my classroom centered around a PC (my build: Windows 10 Pro w/ a GTX 750 GPU), a Yamaha RX-A760, and an Epson EX 9200 projector. The computer sends a signal via HDMI to the RX-A760, which then sends it via HDMI to the Epson. A *separate* hdmi cable directly connects the computer to the 24” Dell IPS desk monitor.

The problem: Suddenly, out of the blue, either putting the projector on standby (with the receiver left on) or turning the receiver itself off turns off the desktop monitor too. It never use to work like that . . . I could work through my monitor with either the projector, receiver, or both off, and had no issues. Windows 10 and the nVidia software are set to see the monitor as the primary, and clone it to the projector. Then one day, 4th period, something changed. I hit the switch to turn the projector to standby - **poof** - no monitor signal either.

Troubleshooting:

1. I’ve tried different combinations. Receiver on, projector off > no signal. Receiver on, projector disconnected > no signal. Receiver itself off > also no signal (with or without projector connected)
2. I checked the Graphics settings. All is correct – monitor is primary, cloned to projector
   
3. I did a clean reinstall of the Graphics Drivers, using DDU uninstaller to be sure I got it all
   
4. I made sure that the Epson projector’s Eco Mode is “Communication On”
   
5. I changed cables, and which ports they were plugged into on the GPUI
   
6. I made sure CEC HDMI control is OFF on the Yamaha Receiver

I’m of the inclination that the receiver is somehow the culprit, since if I physically disconnect the receiver itself from the PC, the GPU signal to the monitor returns. But if I physically disconnect the projector from the receiver, the monitor stays dark, leading me to believe it isn’t the projector sending that message. But why?

What the heck gives? How do I fix this?

Any suggestions or help would be greatly appreciated. This system is mission-critical now that school is under way, and I’m at a loss as to what it could be.