Second monitor with iMac

MrNPG

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Hi, so I’ve got my new 5k iMac but having problems with my second monitor that I use.

With my previous old iMac the second monitor worked fine, connected to the mac using a mini display port to HDMI cable.

With my new iMac, i have purchased a USB-C (thunderbolt 3) to HDMI cable but it doesn’t work. I can see an image on the second monitor but it just flashes up for literally a second and disappears.
So, is this because the new iMac is 5k and the second monitor cannot accept the signal?

Do i maybe need a “better” cable that can transfer the signal? Or maybe just the cable i have is faulty?

Has anyone alse successfully connected a monitor to a 5k iMac using this method?

My second monitor’s resolution is 1680x1050 @ 60hz, if that matters?

Cheers.
 
Hi, so I’ve got my new 5k iMac but having problems with my second monitor that I use.

With my previous old iMac the second monitor worked fine, connected to the mac using a mini display port to HDMI cable.

With my new iMac, i have purchased a USB-C (thunderbolt 3) to HDMI cable but it doesn’t work. I can see an image on the second monitor but it just flashes up for literally a second and disappears.
So, is this because the new iMac is 5k and the second monitor cannot accept the signal?

Do i maybe need a “better” cable that can transfer the signal? Or maybe just the cable i have is faulty?

Has anyone alse successfully connected a monitor to a 5k iMac using this method?

My second monitor’s resolution is 1680x1050 @ 60hz, if that matters?

Cheers.
I had some similar issues when I updated my Imac to a 5k model. A Dell U2715H monitor was connected as a second screen. This was done using a USB-C to HDMI adapter and separate HDMI cable. Whilst this setup worked most of the time there were occasional issues connecting to the Dell monitor which were resolved by either unplugging the adapter and trying another output or switching between input modes on the Dell menu screen. Not a major hassle but just enough to be a pain.

I had three different USB-C to HDMI adapters courtesy of having a Macbook Pro (when you enter the Apple ecosystem you end up with a nice collection of adapters 😎) but nothing made much difference. A work colleague let me borrow a USB-C to Displayport adapter and this worked much better, only rarely do I now have to reconnect the Dell monitor.

This behaviour is not just unique to my Imac using HDMI. I often connect my 2016 Macbook Pro to two monitors (Dell U2515H & an ageing Dell G2410). With HDMI I have the same issue as with the Imac, on occasions the Dell U2515H will not display correctly but this is always quickly sorted by unplugging the adapter and inserting it in another output on the Macbook Pro. I never bothered swapping to Displayport because the problem is so easily sorted. Strange that there are never any issues connecting to the old Dell G2410 using a UBC-C to DVI adapter?

It sounds like your issue is the cable and I would try another one or an adapter first.
 
I had some similar issues when I updated my Imac to a 5k model. A Dell U2715H monitor was connected as a second screen. This was done using a USB-C to HDMI adapter and separate HDMI cable. Whilst this setup worked most of the time there were occasional issues connecting to the Dell monitor which were resolved by either unplugging the adapter and trying another output or switching between input modes on the Dell menu screen. Not a major hassle but just enough to be a pain.

I had three different USB-C to HDMI adapters courtesy of having a Macbook Pro (when you enter the Apple ecosystem you end up with a nice collection of adapters 😎) but nothing made much difference. A work colleague let me borrow a USB-C to Displayport adapter and this worked much better, only rarely do I now have to reconnect the Dell monitor.

This behaviour is not just unique to my Imac using HDMI. I often connect my 2016 Macbook Pro to two monitors (Dell U2515H & an ageing Dell G2410). With HDMI I have the same issue as with the Imac, on occasions the Dell U2515H will not display correctly but this is always quickly sorted by unplugging the adapter and inserting it in another output on the Macbook Pro. I never bothered swapping to Displayport because the problem is so easily sorted. Strange that there are never any issues connecting to the old Dell G2410 using a UBC-C to DVI adapter?

It sounds like your issue is the cable and I would try another one or an adapter first.
Many thanks for this, very helpful.
I wonder whether i should try the VGA route? My second monitor only has VGA or HDMI inputs so maybe i could try a usb-c to vga cable?
 
Many thanks for this, very helpful.
I wonder whether i should try the VGA route? My second monitor only has VGA or HDMI inputs so maybe i could try a usb-c to vga cable?
If it was me I would try and resolve the HDMI issue rather than use the inferior VGA (analogue) standard. You need to confirm if the issue is with the cable, try a USB-C to HDMI adapter and separate HDMI lead to see if this works. I would only use the VGA option as a last resort.
 
I would suggest you try an apple cable such as this
Often apple computers are picky about what cables will work.
 
So, the vga cable didn’t work.

Back to the hdmi option. I must admit i’m a bit loathe to spend £75 on the official Apple adapter so any recommendations for other ones? Which is the better option, an adapter and an hdmi cable or an all in one usb c to hdmi cable?
 
So, the vga cable didn’t work.

Back to the hdmi option. I must admit i’m a bit loathe to spend £75 on the official Apple adapter so any recommendations for other ones? Which is the better option, an adapter and an hdmi cable or an all in one usb c to hdmi cable?

So a USB-C to VGA adapter and lead did not work? Very strange for both connection options not to work... What is the monitor that you are trying to connect to?

Here is a link to the USB-C to HDMI adapter (ANKER) that I can confirm works with a 5k Imac:
Anker Adapter

On my Dell toggling between the input options would sometimes do the trick and get the monitor to connect. Not all monitors auto detect the input, or at least not in my experience.

You could also talk to Apple support, see what they say because you have just purchased it. May save you some time trawling the internet looking for solutions.

As a last resort you could try the Apple option which is expensive just to test. Apple have the no-hassle money back 14 day guarantee.
 
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So a USB-C to VGA adapter and lead did not work? Very strange for both connection options not to work... What is the monitor that you are trying to connect to?

Here is a link to the USB-C to HDMI adapter (ANKER) that I can confirm works with a 5k Imac:
Anker Adapter

On my Dell toggling between the input options would sometimes do the trick and get the monitor to connect. Not all monitors auto detect the input, or at least not in my experience.

You could also talk to Apple support, see what they say because you have just purchased it. May save you some time trawling the internet looking for solutions.

As a last resort you could try the Apple option which is expensive just to test. Apple have the no-hassle money back 14 day guarantee.

My monitor is an HP w2207h, it must be at least 12/13 years old now, but worked fine with my previous 2009 iMac, connected via Mini-display port to HDMI cable.

I've ordered the following adapter earlier today, should arrive tomorrow, so will give that a go.

Amazon product ASIN B01N6DCH1K
 
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Well the Choetech adapter didn’t work either so I’m guessing that my old HP monitor is just not compatible with the new 5k iMac.
 
I wonder if this is due to the HP W2207H's native resolution of 1680 by 1050 as this isn't HD resolution scaled in any way. You're better off with new monitors and benefit from the lower power consumption.
 

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