I know this has been discussed before but my Roku Ultra Model 4640X refuses to stay stable on 4k resolutions (and sometime even 1080p). A blank screen or the HDCP error message happens almost every time I try to use it. I will attempt to list my remedies which have not helped. Equipment is the ROKU connected to a Denon S930H receiver and a Vizio P55C1 TV. All inputs on both the receiver and TV are the latest specifications for 4k HDR 60HZ. If I bypass the receiver it fails less but still is not stable and fails after about 10 minutes. I have changed HDMI cables several times. When from Amazon basic cables to Monster cables to Monoprice cables all spec'ed for HDR 4k 60hz. Swapped from one brand cable to another same brand and then to different brands changing cables about two dozen times with no success. Changed every display option in the menu also to no avail. Firmware is also latest. I also hooked the Roku up to a Samsung UN43MU6300 TV and had the same results. I am about ready to toss this thing. Is the new ROKU + any better? Maybe I should just replace it.
2. buy one of these HDMI cables. Long story short, your are probably passing more than 18 gbps and need a cable that handles that. These are capable of 48 gbps. Belkin Ultra HD High Speed HDMI Cable ECHOGEAR Braided HDMI Cable
if you don't want to do both you can try to lower chroma subsmpling. from 4:2:2 to 4:2:0
Tried all options, still ng. I have a 18" heavy certified 18 MHZ cable. Changed cables more times then can count. Have Shield TV that works fine. Now at times snowy pictures comes up and then sometimes black picture. My model is 4640x. See the present ultra is higher model number. Maybe they changed something on the newer model. Time to throw this thing out! I won't buy a Roku again!
The model 4640 was discontinued and replaced by the 4660 in early October 2017. Did you buy the 4640 after the 4660 was released? Or was it the current model when you bought it? If so, has it been working correctly all this time and just started behaving this way? When did the problem begin?
Basil https://www.basilsblog.com/ Roku Ultra (4660) Apple TV (5th gen), TiVo
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