I have a roku 4200X connected to a Samsung TV. When it gets hot outside the roku picture will start to flicker after about an hour of viewing and then totally scramble to black and flickering lines. Only happens in summer when hot outside - inside is always ac controlled to 74. Switching to broadcast TV fixes the picture immediately. Switching back to roku input then goes back normal for a few minutes and problem starts over again. Never happens in winter. I live in Houston and it does get supper hot, but can't figure out how that is affecting the roku or roku picture. Never happens with broadcast TV or DVD. Roku is connected via Ethernet to router just 3 ft away. Have Xfinity high speed internet and not similarly affected on other devices. Just with roku. Has been happening the same way for years... Every hot summer roku starts to flicker after an hour or two of watching and then goes to a full blown scrambled mess. Any ideas?

I would try the following...

• Use a different HDMI cable.
• Use a different HDMI TV port.
• When everyone's ac is running, the incoming voltage from power lines can drop.  This might cause issues with your Roku power supply suppling correct voltage to the Roku.
• Maybe hardware issue and time to upgrade Roku.

Thanks. Already tried the first two. Don't know about the third mostly because it doesn't start flickering until I am watching for an hour or two. Seems like if it were a issue with the grid voltage that it would occur randomly, not always after an hour or more of watching. Sounds like maybe the fourth is the way to go. Just don't want to pay for a new roku and have the same outcome.