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ATI HD5850 intermittant black screen on PC monitor when Onkyo608 is on


I have an issue with the Radeon HD5850 (software ATI Catalyst Control Centre 10.12) and onkyo 608.

The setup:
I have my pc attached to a monitor (via dvi port on the ATI graphics card), and the onkyo attached with a hdmi cat 6 extender (via hdmi port on the graphics card). The hdmi extender needs to be powered on to transmit the hdmi signal to the onkyo.

The problem:
My PC monitor blinks black for about 4 seconds and then is ok for about 16 seconds and then goes black and ok again (this repeats randomly, going black about once a minuite). This only happens when the hdmi extender is turned off and the onkyo is being used.

This black screen is similar to the black screen when i have logged in to windows, when i assume that the ATI CCC has loaded up.

My guess:
I think this may be an output or display auto detect problem, and the CCC is constantly detecting my monitor or changing the settings of it. Does anyone have any advise on how to stop this happening?

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  1. Best answer
    The HDMI port is losing the +5V supply which is limited to 50mA when you turn off the repeater.

    When that collapses the other port also goes down and that's when you get the black screen almost similar to No-Signal Condition.

    Try to simplify your connection that is without a repeater:

    Here's my connection using 4890 DVI Port to Denon HDMI PORT:

    DVI-PORT->ATI/HDMI Converter->HDMI Cable-> Receiver HDMI Input

    My HDMI cable is 25ft long. I get the audio and video to my receiver without the need for a repeater.

    If you really have a long HDMI cable then you may need a repeater.
  2. Here's an info on HDMI for additional reference. Long cable compromize the diiferential signals.
  3. thanks leon,

    i didnt buy a long HDMI cable because i thought that:
    they were expensive
    lost signal over long distances.

    However, the amount I spent on a hdmi extender and two cat 6 cables 25m in length was probably the same as a 25m HDMI cable in the end. I hope the signal is good - i havent checked the picture quality as i dont have a tv attached to my onkyo yet.

    I will take your advice, and leave the hdmi Cat6e extender on at all times (this looks to have resolved the problem)

    Many thanks!
  4. Best answer selected by laxmanstretch.
  5. This topic has been closed by Mousemonkey
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