Problem: Our new LG G3 TV was turning off after 15 minutes when the HDMI switch is set to the Spectrum DVR. It worked fine when the HDMI switch is set to the Apple TV 4K. It seemed to be some sort of interaction between the TV and the DVR.

Configuration:

• HDMI 4-port switch box
• LG G3 TV (HDMI port 4 to switch box output)
• Spectrum DVR (Magnavox) (input port 2 on switch box)
• Apple TV 4K (input port 3 on switch box)
• All cabling is Ultimate HDMI, suitable for 8K, in wall rated.

Googled several things. Various solutions presented. None worked.

Things we tried:

• Checked all the TV timers, the sleep timer is indeed set off.
• Switched the HDMI cable between the DVR and the switch box to an Ultimate HDMI cable. The entire path is now Ultimate HDMI.
• Unplugged the TV for 5 minutes, pressed the power button for a minute, and plugged it back in.
• Turned off the HDMI-CEC (LG SIMPLINK). It turns itself back in a second or two.
• Unplugged the spectrum DVR, waited 5 minutes, plugged it back in.
• Checked all the DVR settings, none of the timers are set for 15 minutes.

None of the above Googled solutions included multiple inputs through a switch. It turns out that the Apple TV 4K sleep timer was the issue. It was set for 15 minutes. Even though the switch box was set to the DVR, the HDMI-CEC settings of the Apple TV caused the TV to shut down when the (disconnected) Apple TV went to sleep. Somehow the Apple TV was communicating control even though the switch box was set to the DVR.