2017 iMac 27 connecting to external displays

I then picked up an Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter to use with the DisplayPort to DVI Adapter.

Guaranteed not to work.

https://support.apple.com/HT207266

"The Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter doesn't support connections to these devices:

• Apple LED Cinema Display
• DisplayPort or mini DisplayPort displays
• DisplayPort or mini DisplayPort adapters, such as Mini DisplayPort to HDMI or Mini DisplayPort to VGA adapters"

Have you tried contacting StarTech? It may be that the 2017 iMac doesn't support USB-C Port DisplayPort ALT mode, which may be needed for those adapters.

Belkin makes a HDMI adapter

http://www.belkin.com/us/F2CU038-Belkin/p/P-F2CU038/

that is compatible withg the 2017 iMac. You can the use a HDMI to DVI adapter, which should work because HDMI and DVI use the same video signals.

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. = AllSmartLifeusb 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....

I have the new 27" iMac and have 2 27" LG 5k monitors hooked to it and not having any problems. Had the same 2 monitors hooked to the MacBook Pro 15" 2016 and sometimes it would flicker and I had to shut down the MacBook. LG has a screen manager app for the monitor that runs in the background. It checks for firmware updates an does a few other things too. I read that there was a firmware update for these monitors. After installing the app on both Macs no problems. As for hooking other monitors to the iMac... i don't know.

Apple how to use these monitors on your Mac:

Use the LG UltraFine 5K Display with your Mac - Apple Support

________________________________________________________________

LG info on these monitors:

http://www.lg.com/us/monitors/lg-27MD5KA-B-5k-uhd-led-monitor

________________________________________________________________

LG screen manger app:

http://www.lg.com/us/support-product/lg-27MD5KA-B#manuals

$1,700 CDN is about what the US paying for these monitors when converted to USD. We're spending $1,299 for the monitors here. I bought the 2 monitors before March 1st. Apple had them on sell for $999.00 if you brought them before March 1st. After March 1st they went up to $1,200. $999 USD = $1,299 CDN.

As for hookup... using the thunderbolt 3 connection. You need a HDMI dongle from thunderbolt to make that work. I have one... I also have a dongle for my 2016 15" MacBook Pro that has HDMI, card reader, thunderbolt 3, USB C and 2 USB. Something like this...

Good luck - if you indeed get the same StarTech adapter as I did, you will be in great shape. You connect direct from the octopus cable that comes with each ACD 23. Do check back and let us all know. I am enjoying the setup enormously. Here is the image of my set up that didn't load previously.

I'm trying to do the same as you and snp.ltd: connect an ACD 23" to a 2017 iMac. I initially bought a DVI->USBC adapter on Amazon (Belinda) but only could get the iMac to recognize it a few times (saw the display in system prefs) but the ACD would only have a black screen and the white light on the front of the ACD would flash on and then off. So I called StarTech to see if their adapter is actually any different and the very helpful agent there said it is hit or miss with the ACD's that have a built-in DVI cable due to a proprietary timing issue that Apple used rendering only Apple's adapters reliable.

So I'm curious, skybax, do your ACD's have the built in DVI cable? Don't want to order the StarTech if I don't have the exact same situation as you do, though glad you got it all to work. I'm hopeful.

Sadly though I don't see a DVI->USBC adapter in Apple's store.

My 23" ACD looks like this:

I finally found a solution to my problem trying to connect a 23" ACD to a 2017 iMac. The great support people at https://www.monoprice.com helped me to understand that the particular year of ACD I have is the culprit as Apple's timing built into the attached DVI cable to it is proprietary and ONLY Apple connectors will work. So if you have a cinema display with the cables on the back looking like the image below you will have to buy the following 2 connectors to make it work. I got them yesterday, connected everything and my ACD is working perfectly with my iMac.

Apple HDMI to DVI Adapter - Apple

and

USB-C Digital AV Multiport Adapter - Apple

It's a pricey solution but it works if your ACD looks like this on the back:

I have similar issue but on iMac 27 late 2013 with ThunderBolt2 and Cinema Display HD (aluminium case not LED). Connected. When I startup my Mac every morning the second monitor still black and the little power led doesn't start. A need to unplug from the ThunderBolt port, wait three seconds and plugin again. Only with this way I can see the second monitor turned on :-(

As said I think is a power up problem and the TB2 doesn't wake up the monitor from power standby.

I hope for a solution because the ACD is anyway a good display.

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.

I have the same situation as you do. Just got a new mid-2017 iMac 27. I want to use two 23-inch Apple Cinema HD Displays (M9178LL/A; 1920 x 1200 pixels). Based on your suggestion and other research, I ordered the StarTech USB-C to DVI adapter. Hopefully it works like you say. I have used these originally very expensive displays with Mini DisplayPort adapters for both a MacBook pro 2015 and a mid 2010 iMac. I had forgotten that these are actually DVI displays (not Mini DisplayPort), thus you really need to replace the DVI to Mini DisplayPort adapter with a DVI to USB-C adapter as stated in Adapters for connecting a display to the Thunderbolt 3 (USB-C) port on your Mac - Apple Support. I misunderstood that the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter was the easy solution. I falsely assumed that you could plug the MiniDisplay adapter into the Thunderbolt 2 port as I do with the MacBook Pro or the Thunderbolt port in the old iMac.

2017 iMac does not support TargetDisplay.

http://appleinsider.com/articles/17/06/15/2017-4k-5k-imacs-wont-support-target-d isplay-mode-despite-thunderbolt-3

I am able to connect a 2010 iMac as Target Display to a 2015 MacBook Pro using Mini Display Port to Mini Display Port cable. Just to verify what the article says, I could not connect 2010 iMac it to 2017 iMac using the USB-C to Thunderbolt 2 adapter with same cable (Mini Display Port to Mini Display Port cable). See Use your iMac as a display with Target Display Mode - Apple Support

mscastleman wrote:

Would this or something like this work to allow me to connect a iMac (Retina 5K, 27-inch, Late 2014) to my new 2017 5K iMac?

I want to use the older iMac as an additional monitor

No.

https://support.apple.com/HT204592

"iMac (Retina 5K, 27-inch, Late 2014) and later iMac models can't be used as Target Display Mode displays."

docari wrote:

Has anyone had luck connecting the 27" Apple Thunderbolt display to the new iMac 2017 as a second monitor? If so, which adaptor has worked? If anyone has some opinions on good 27" monitors that can mesh well aesthetically with the iMac, connect reliably for ~$500 please let me know! Leaning toward an old Thunderbolt display but wanted to see if anyone has connected it and if there are better options out there! Thanks!

A Thunderbolt display should work with a Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter

https://www.apple.com/ca/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbo lt-2-adapter

Is says they are compatible.

https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt- 2-adapter

"In addition, it can be used to connect Thunderbolt-enabled displays — such as the Apple Thunderbolt Display"