179      iPhone_iPad_Mac_apple

2017 iMac 27 connecting to external displays

I'm trying to set up a new 2017 iMac for a friend, and I'm having trouble connecting an external display to it. I first tried connecting an LG Ultra Fine 5K display using the supplied cable. It worked for a few minutes, and then it started flickering until it just blacked out. I tried a different cable (Belkin Thunderbolt 3) with no luck.

I also connected it to a ViewSonic 4K monitor through the Display Port using a Display Port to Thunderbolt 3 adapter. That monitor wouldn't even come on.

The weird part is that he was using both monitors with his 2016 MacBook Pro (has since sold), and they worked fine.

I have tried restarting as well as just shutting the iMac off before plugging the monitor in, even though I know I shouldn't have to. To be clear, I have only plugged in each monitor separately and never both at the same time.

I am at a loss. It appears to be an issue with the iMac itself, but I thought I'd post here in case this has happened to someone else and there's a fix, or I'm doing something wrong. Thanks in advance for your help.

The specs for the iMac - 4.2 GHz Core i7, 64GB RAM, Radeon Pro 580

to All who read this.

I am happy to report that I hooked up the

to my 2017 iMac USB-c port and the Display port on the Dell P2715Q 4K 27 inch monitor,

and......

drum rolll......

IT WORKS!!!! just like it is supposed to.

for those of you not reading my previous post above, here is what I ordered from Amazon:

CHOETECH USB-C to DisplayPort Adapter Cable 4Kx2K@60Hz (4ft/1.2m) for 2017 iMac, 2017

it was only $20!

Now what to do with extra USB-c to Thunderbolt adapter I paid $50 for....

Have you tried zapping the pram command+option+p+r after you hear the startup chime until you hear the startup chime a second time. I have a 2017 27" imac which I'm about to start trying to connect to an external monitor via Thunderbolt 3 to displayport adapter. When Macs get confused, the PRAM stays confused until you reset it.

Thanks for your help! Zapping the PRAM doesn't appear to have worked, but does your 2017 iMac have a startup chime? This one is as quiet as the 2016 MacBook Pro. I've tried: sudo nvram BootAudio=%01, but no luck. I'm used to waiting for the chime and then second chime like you said, but without one I just went by the light of the screen.

Were you able to get your external monitor connected successfully?

I have had a similar issue with a brand new iMac 27". No signal detected using a USB 3.1 Type C to DisplayPort 1.2 UHD adapter (made by Club) to a brand new BenQ BL2711U.

Reading many posts, it seems hooking an external monitor to this computer has been a nightmare.

As you can see from Apple's website the USB-C Digital AV Multiport Adapter has a rating of 2 stars.

If anyone out there can recommend a flawlessly working adapter to connect the new iMac to an external monitor (HDMI or DisplayPort), it would be very much appreciated.

Cheers,

Jason

Doh! No pram zapping chime. No chime at all. I just attempted to connect a 27" IPS dual link DVI display to my 2017 iMac using Apple's dual link DVI to mini-displayport adapter and a Thunderbolt 3 to mini-displayport adapter https://amzn.to/2upHYem which >>>>>DID NOT WORK<<<<<<.

Prior experience with Macs leads me to be philosophical. Pram zapping is critical to getting mini-displayport working well. And the fact that we have no pram zapping now leads me to *HYPOTHESIZE* that we've got a firmware update coming that may restore pram zapping. I have no data. Just from my experience working at Fortune 50 US tech company and my observing the section managers shipping firmware **** to secure their ship date bonuses, and then the real firmware releases in 6 more weeks. I was not at Apple. Again, I have no data. Just suspicions based on somewhat related experience.

And I'm going to try your Sudo trick and see if that works. Thanks for that! :-)

billm

I've now attempted to use the Apple Thunderbolt 3 to Thunderbolt 2 adapter MMEL2AM/A US$45 + tax again with no luck. Plugging in the Apple mini-dvi to dual link DVI adapter to the TB3toTB2 does not elicit a *flinch* from the 2017 iMac18,3. The Apple mini-dvi to dual link DVI works fine, as tested on my MacbookPro9,2 Still hoping for that firmware update!!! ~billm

I have similar issue.  Just got my new iMac with same config as yours (except less RAM) and the Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter.  I have been successfully using a Dell P2715Q 4K 27 inch monitor with my 2015 MacBookPro via Thunderbolt 2 to Display port.  but not with new iMac.  Spoke with apple support who didn't have a clue (at least it only took half hour). Then spoke with Dell Monitor support.  After being passed around 4 times, spent total 1.75 hours with no good result. 

Then, this morning found this article in today's NYT:

Expanding Your View Beyond the Laptop Screen - The New York Times

which references this support article:

Connect external displays to MacBook Pro (2016) - Apple Support

in this support article they reference "4K display that supports 4K at 60Hz"

then it says "This display requires a third-party USB-C to DisplayPort adapter or USB-C to HDMI 2.0 adapter. The Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter doesn't support this display."  Sure wish the Apple Clueless "Genius" who sold me the Apple adapter at $50 knew this. grr.....

Then I went to Amazon and searched for "USB-C to DisplayPort adapter".  et Voila:

Amazon.com: CHOETECH USB-C to DisplayPort Adapter Cable 4Kx2K@60Hz (4ft/1.2m) for 2017 iMac, 2017 MacBook Pro, 2016 MacB…

I have ordered this cable and will know by Saturday if it works.

Long winded response but hope this makes sense and is helpful to you and others who are having same issue.

Thanks for the excellent information. After taking my iMac (and my LG 5K display) to the Genius Bar, I figured out that the LG display suffered from the WiFi router issue. It worked because it was further away from the router. Unfortunately, moving it far enough away isn't viable now, and it shouldn't do that anyway. So I sent that to LG's repair service.

My other monitor that does not work is a Viewsonic 4K monitor. I used a Cable Matters USB-C/Thunderbolt 3 to DisplayPort 4K 60Hz Adapter that I bought from Amazon. This adapter worked great with a late 2016 MacBook Pro. Obviously, something has to be different with the TB3/USB-C ports on the new iMac or my cable/adapter died all of a sudden.

I'm hoping you have luck with the CHOETECH cable you bought.

Still hoping for that firmware update!!!

Me too!

My EIZO monitor is DVI and connected to my old iMac with a DVI to display port adapter. No Tbolt3 to 2 adapter could get it to work with my 2017 iMac. After getting an OWC Thunderbolt 2 equipped enclosure my display connected just fine.

I'm in a similar boat - have newest iMac 27 18,3 maxed out and want to connect 2 Apple Cinema Didplay 23 inch monitors. Has anyone successfully gotten an old Cinema Display to work with a new 3017 iMac?

Thanks to ownry for the link that told me I would be wasting my money with a Thunderbolt 3 to 2 adapter going to a dual link DVI monitor. Here is ownry's link again:

Connect external displays to MacBook Pro (2016) - Apple Support

Here is the section on DVI (with most excellent Evernote Skitch rectangles around the "WILL NOT WORK" sentence).

So in addition to the Apple thunderbolt 3 to 2 adapter not working, I can add one more adapter (repeat from my post above) that does not work (yet, still firmware-fantasizing) to dual link DVI monitors. = AllSmartLife usb c to mini displayport.

to All who read this.

I am happy to report that I hooked up the

to my 2017 iMac USB-c port and the Display port on the Dell P2715Q 4K 27 inch monitor,

and......

drum rolll......

IT WORKS!!!! just like it is supposed to.

for those of you not reading my previous post above, here is what I ordered from Amazon:

CHOETECH USB-C to DisplayPort Adapter Cable 4Kx2K@60Hz (4ft/1.2m) for 2017 iMac, 2017

it was only $20!

Now what to do with extra USB-c to Thunderbolt adapter I paid $50 for....

Congrats!  Must be nice. How do they compare when side by side?  Your solution won't work with my 2, 11 year old Cinema displays!

And I can confirm the same CHOETECH cable works for a 2-year-old Viewsonic VP2780 UHD 4K monitor.

Thank you very much ownry, billm, and everyone else!

最后更新：2017-09-01 02:03:07

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