Awhile back, a friend was downsizing before a move and gave me a Roku 3 with the plastic still on the box and remote. I set it to my account and put it away as a spare. I ran across it last week and decided to reset it and get it to someone who could use it.
Over the weekend, I was testing and resetting a couple of other streaming devices and, when I got to this one, it was acting weird. I gave up and started again today. At first, it seemed to be rebooting after the splash screen played for a bit. Then, one time, it completed the boot process and got to the main screen. I was setting up the WiFi password and, as I got to the last character, the screen went black.
Since then, I’ve tried the reset button several times (sometimes with HDMI plugged in, sometimes with just the power), have switched HDMI cables, and tried a second TV, different power strip and different wall outlet. While trying it with the second TV, a single time it came up with a weird green lined screen with nothing readable Since that, the TV shows no signal at that source or when switched to the other HDMI input.
You can try a factory reset. Locate the reset button under the power connector and with a paperclip or something similar press and hold it for no less than 30 seconds with the power connected.
If that doesn't help, I would next suspect the power adapter. I'm pretty sure the Roku 3 uses a 12V adapter. It's unlikely you have another lying around that you can try, but they can be had fairly cheaply. Some might argue that it's not worth putting time and money into a Roku 3, but mine still works just fine.
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