iMac 27" 2017 HDMI / DP Issue

You have 90 days of complimentary AppleCare telephone support with your 2017 iMac. If you were not aware of this program please review Apple Complimentary Support. This seems like the ideal time to use it.

Maybe this'll help:-

Using 4K displays, 5K displays, and Ultra HD TVs with your Mac - Apple Support

Look at the section called Multi-stream transport (MST) displays (about half way down). It seems like some monitors need you to configure them in their own Control Panel (Dell is one of the examples specified).

Hi, I have a simliar issue.

I just received my iMac 27 5K with radeon 575 card, and I was expected to be able to use an USB-c adapter (https://www.amazon.co.uk/dp/B01AA5TSGQ/ref=cm_sw_r_cp_dp_T1_G1mqzbZFY49TH) to connect my Dell P2715q but nothing happens.

The adapter works fine with Macbook pro 2017. So I guess I have the same issue that you have.

I will try and contact Apple and use their Complimentary Support and see what they say.

I’m having similar issues with my 2017 27-inch iMac. First I thought it was because of a faulty adapter, but I’m starting to think it’s the iMac’s problem. I don’t have any other USB-C machines to test the adapters, but I doubt I got two bad adapters in a row. The cables and displays are otherwise working fine with other computers, so those aren’t the problem.

WORKS:

iMac 27 2017 -> Thunderbolt 3 to 2 adapter -> Apple Thunderbolt Display

DOESN’T WORK (No signal):

iMac 27 2017 -> USB-C to DVI adapter -> Apple Cinema Display

iMac 27 2017 -> USB-C to DisplayPort adapter -> Dell P2415Q (Mini DisplayPort in)

Hi guys - I asked this question in another thread but no-one answered :-( Maybe some kind soul here could check it for me...

I've been thinking about purchasing an iMac Pro or maybe a Mac Pro so I called into my Apple store to look at some of their iMac Pro's. When reading the system specifications, the 27 inch models all boast a 5K Retina display, offering 5120x2880 resolution - however...

When I open the System Preferences and try to adjust the screen resolution, the highest resolution offered is only 3200x1800 :-(

Is that the same for you guys or is there some way to use the extra screen resolution ??

Update:

I tried an integrated adapter cable instead of plugging a cable into an adapter dongle, and it worked. Seems like the 2017 iMacs are having problems with adapter dongles, even though they worked on recent MBPs.

WORKS:

iMac 27 2017 -> Thunderbolt 3 to 2 adapter -> Apple Thunderbolt Display

iMac 27 2017 -> USB-C to DisplayPort adapter cable (Plugable) -> Dell P2415Q

DOESN’T WORK (No signal):

iMac 27 2017 -> USB-C to DVI adapter -> Apple Cinema Display

iMac 27 2017 -> USB-C to DisplayPort adapter -> Dell P2415Q (Mini DisplayPort in)

Call again and speak to another engineer and if that does not work, request to speak to a senior advisor.

I have the 2017 iMac with the 580 card, trying to use a USB-C (thunderbolt 3) to HDMI cable to a 4k tv and I get no signal.

same problem here, can't connect my iMac 5k 2017 to my Dell Monitor 😟

The iMac not recognize the monitor. I don't know what I do