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Video output as HDMI via TB-back panel fails - why?

M

macerkopp

macrumors newbie
Original poster
May 20, 2022
11
0
For some reason I wanted to connect my external monitor with it`s HDMI input onto my M4max. Meanwhile I tried several cables or adapters, but no chance to get an video signal via HDMI onto my monitor. All the testet adapters or cables work properly with an iphone or ipad - but no chance to get a video signal from the macstudio. Where is the difference between the usb-c output of an iphone compared to the output of a mac? I read a lot about of the need of "displayport alternate mode", but I think this shouldn`t be an issue for the MacStudio?!

Tried it with an M1max and an M4max, with the same disappointing result. Any helpful thoughts or advices for me?
 
Here is Apple's article on connecting displays:

Connect a display to Mac Studio

Connect external displays to your Mac Studio.
support.apple.com support.apple.com

This support article addresses dark displays:

If your external display is dark or low resolution - Apple Support

If your Mac is working, but the external display connected to it has a blank or black screen (no video) or can't use its highest resolutions or refresh rates, try these solutions.
support.apple.com support.apple.com

It says, "Your external display will be dark or use a lower resolution or refresh rate if you configure it to exceed the maximum supported resolution or refresh rate."

Could this be your problem. Also, have you tried turning up the brightness on the display?
 
joevt said:
Which MacStudio? Some have USB-C ports that are not Thunderbolt ports.
Click to expand...
As written: checked it with an M1max and M4max. Used the TB-ports of the back panel. All these ports should deliver a video signal, on the contrary to the front panel connectors.
 
Last edited:
chabig said:
Here is Apple's article on connecting displays:

Connect a display to Mac Studio

Connect external displays to your Mac Studio.
support.apple.com support.apple.com

This support article addresses dark displays:

If your external display is dark or low resolution - Apple Support

If your Mac is working, but the external display connected to it has a blank or black screen (no video) or can't use its highest resolutions or refresh rates, try these solutions.
support.apple.com support.apple.com

It says, "Your external display will be dark or use a lower resolution or refresh rate if you configure it to exceed the maximum supported resolution or refresh rate."

Could this be your problem. Also, have you tried turning up the brightness on the display?
Click to expand...
The monitor is not only "dark" but there is no video signal existing! I`ve been doing some more research also via ChatGPT and I think to understand that the mentioned "DP alt mode" seems to be the issue. So the specific signal way from TB to HDMI seems to need very special "active" cables that are able to take MacStudio`s output signal and to deliver it as "DP alt mode" to the monitor. There are such specific cables on the market that claim to be "DP alt mode" compatible - but very few and significantly more expensive (20-40€) compared to the huge numbers of "Thunderbolt to HDMI" you can find at A. with prices of 7...15€. That`s finally is my suspicion why "normal" cables, what are working properly from Iphone or Ipad to the monitors HDMI port, are not working on the (modern) Mac. But who am I to understand that stupid mess in the whole USBC, Thunderbolt or whatever standards....

The reason for all my efforts in such solution via HDMI was that I can control the input in my monitor from two different Macs via a convinient HDMI switch instead fiddling in the back of the monitor via monitors menue to swich the input ports. But finally I`ve the feeling this will be the best way to.....
 
Another "Fishrrman dumb question™":

If the display has HDMI input, why not use a connecting cable from the Studio's HDMI OUTput? (unless it's already in use)
 
Fishrrman said:
Another "Fishrrman dumb question™":
Click to expand...

No dumb, but very reasonable question ;-) Did it before but got frequently 1-2 sec lasting blackouts on the screen what was very annoying. Such issues are reported often, particularly when it`s about connecting an extern DELL-monitor to a Mac. Because this doesn`t happen with a video cable between TB-output to USBC-input , I thought give it a chance if a cable TB-output to HDMI-input can solve that issue.
But as reported: with this plan I ran into other problems; wouldn`t have expected that it can be that tricky....
 
I have HDMI to HDMI (Dell U2715H), and USB-C to DP via adapter (Dell U2715H) on M2 Studio….. 🤔
It could be your cable or maybe too high refresh rate on the monitor.
 
If the Studio doesn't have a working display, you can enable screen sharing, then share the screen on a different computer to see if the MacStudio detects the non-working display. If the MacStudio detects the non-working display, then note what resolution it is trying to use. Select a different resolution.

Can you link one of the cables you are using?
 
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I'd go back to the HDMI-->HDMI cable.
Try "switching it around end-to-end", too.

I'd also try installing the "BetterDisplay" utility.
It may give you more control over the display since it can work with all the display's "ddc" capabilities. Perhaps there's a setting in there somewhere that could eliminate or at least reduce the blackouts (which might be the result of the display losing "such" with the Mac's video signal).

BetterDisplay operates in both a "free mode" and a "paid mode".
The free mode may be "all you need":
github.com

Releases · waydabber/BetterDisplay

Unlock your displays on your Mac! Flexible HiDPI scaling, XDR/HDR extra brightness, virtual screens, DDC control, extra dimming, PIP/streaming, EDID override and lots more! - waydabber/BetterDisplay
github.com github.com
 
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