8

MacBook Pro (15-inch, 2016) with 2 USB-C to HDMI adapters. The setup works great if I start up in that configuration.

If I connect the adapters while the machine is running or simply sleeping, one of the monitors will never get a signal and stay in low power mode. The OS sees the monitor, it shows in the display arrangement settings and I can move the mouse into it, but until I restart, I can't see anything on it.

Once I have restarted I can let the machine sleep or whatever, and the display still works unless I disconnect the adapter. As soon as I do that a restart is required to use it again.

Using MacOS Sierra (10.12.4)

Using this adapter: https://www.amazon.com/gp/product/B01IUXA9YK/

  • Are you using Apple's adapter or a third party one? If it's third party, which brand and model? – NoahL Apr 22 '17 at 4:34
  • In addition to answering @NoahL 's questions, can you clarify which exact model of 2016 MBP you have? – Monomeeth Apr 22 '17 at 5:47
  • Just to add a real-life experience: I'm using 2 USB-C to DisplayPort adapters (which are basically similar to the HDMI adapters) - and this works without any problems in that regard. Several times a week I plugin in both monitors after the MacBook Pro is booted (basically I never turn it off) - removing the cables again also never give problems. – jksoegaard Apr 22 '17 at 8:24
  • What monitor are you using? Does it have ports other than HDMI? – Allan Apr 27 '17 at 0:15
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The video signal on the Thunderbolt connection on your MBP is actually Display Port so you are actually going from Display Port to HDMI. I am not a fan of converting signals because it's flaky at best.

If you must connect to HDMI, try an active1 adapter like the TRENDnet USB-C to HDMI 4K. They have two versions - one that does 30Hz and another that does 60Hz (it's the Power Delivery version).

What is preferable, is to go from USB-C to Display Port which is actually Display Port to Display Port, so no there's conversion involved. No conversion means less points of failure.

jksoegaard's comments provides more evidence of this:

Just to add a real-life experience: I'm using 2 USB-C to DisplayPort adapters (which are basically similar to the HDMI adapters) - and this works without any problems in that regard. Several times a week I plugin in both monitors after the MacBook Pro is booted (basically I never turn it off) - removing the cables again also never give problems


1 I wrote an answer on this very topic: Passive vs. Active Adapter

1

Update to latest OSX version (10.12.5 (16F73)) fixed the problem.

  • I am on 10.14.5 but this problem still exists. – Bunny Rabbit Jul 10 at 5:29
1

To the above answers, I can't use a USB-C to HDMI active adapter as Macbook pro provides only two USB-C ports. I don't know how a company like Apple comes up with a crappy design like this. I use 2x of this adapter: https://www.amazon.com/gp/product/B07NDH6DRN/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

1 HDMI works perfectly. 1 HDMI needs a restart every time to work (exactly the same problem as described in the question).

I'm running on the latest OS version: 10.14.5

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