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HDMI signal drops and reconnects (Mac) - DC plz help!!1

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I run a Mac Mini connected to two displays. The first is a DVI monitor (connected via a Thunderbolt to DVI adapter) and the second is a TV, directly hooked up to the HDMI out. I mirror the display to the TV to watch movies. The TV conked off a week back and was replaced.

The problem I'm facing after changing TV sets is, when I'm using the TV with the cable box or Playstation, the computer monitor starts blinking every few seconds, a solid black screen, similar to what one sees when changing resolution.

The blinking occurs twice about a second apart, every 15-20 seconds.
Observing the display options menu, I noticed that immediately after the first blink, the menu item for the TV disappears (because the Mac can't see it) there's another blink soon after when the TV gets detected and appears on the menu. It stays that way for 15-20 seconds and then the process repeats.

I've googled around and am at a total loss, I don't even know if the culprit is the Mac or the TV.
I've played around with the power consumption options on the TV, disabled mirroring, selected the "Use as separate display" option on the Mac - none of it made any difference.

When the display is being mirrored, it doesn't blink at all, steady on both ends, so I assume the HDMI cable (10 meters) is ok. Should I opt for a 5 meter high speed cable? Totally out of ideas, the only thing that works for sure right now is to pull out the HDMI cable from the Mac every time I'm not mirroring the display but that's a pain.

Edit: If I'm using the TV for Playstation or cable and power it off (standby), the monitor keeps blinking even when the TV is on standby.

First some generics regarding cables:
Keeping cables as short as possible is always a good strategy. After all, the longer any cable is, the more chance you have it picks up interference.
After that, keep cables that carry mains separated from cables that carry data (again, interference).
Make sure that cables aren't strained in any way, internal shielding becomes compromised and generates a lot of interference on these strains in the best case scenario. Worst case scenario is a potential fire hazard.

Over-provisioning a cable might be a good thing too. if your devices have an output of a certain resolution at a certain frequency, it is a good thing to use a cable between these devices that supports certain resolution+n and certain frequency+n.

About your situation:
From your description I gather that the Mac is the problem. It gets confused when a device is connected on its HDMI port that doesn't want the signal.

If possible, swap the TV and the monitor on the Mac. Does this change the behavior?
Check for irregular behavior between versions of HDMI standards (Wikipedia). After all, there are only 6 of those standards by now. So you might need to replace the HDMI cable anyway to better match the HDMI version(s) your devices are using.

I have had similar strange behavior with displayport and hdmi.. there was no solution.

Shades, the mac worked just fine with the previous TV, same settings, same cable.

Swapping the devices would require me to buy two separate adapters - one HDMI to DVI (or VGA) and a Thunderbolt to HDMI, doesn't really seem worth it.

What I ended up doing was getting an HDCP compliant 3-1 switch, it's arriving in a couple of days.

An explanation from someone who replied on another forum:
The solution for some with handshake issues was to stick a little box between the Mac and HDTV or AVR that retains the correct EDID information, fooling the Mac into thinking it still is actively connected to the display. The Gefen HDMI Detective was a popular model, here's one at Amazon that might work:
--- End quote ---

I ordered a generic pigtail switch (before I read that reply) and not the item mentioned above. If it solves the problem, great. If not, I could use the switch to change to a null output when I'm not mirroring. If that fails too (like the box not allowing me to switch to a null output when there's a live one present) I could just manually plug the cable in and out of the switch rather than the TV or mac, till a better solution comes along.

Replacing the cable seems like the next viable option. And it's also been suggested that I put an Apple TV as an intermediary.

Thanks for the input, Shades and mouser.  :up:

that's a clever idea -- let us know if it works.


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