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gowanis

macrumors 6502
Original poster
Sep 22, 2007
413
7
Just bought the LG 27UD69P-W 4K display to add to my new 5K iMac. I am using a USB-c to displayport cable purchased from Amazon (cable has all good reviews). I have the display working, but when I boot, it doesn't come "on". Mac OS recognizes the display, but it seems I need to unplug from thunderbolt port, and then plug back in to get it to come on. Any ideas what might be wrong here?

I also want to add, that side by side, the iMac is significantly brighter. Is there a likely brightness issue with the LG, or am I just spoiled by how awesome the iMac 5K display is ?
 
Last edited:

chscag

macrumors 601
Feb 17, 2008
4,622
1,946
Fort Worth, Texas
Just a WAG here.... it sounds like the LG is sleeping until a video signal wakes it. Unplugging and then plugging the cable back in likely wakes it up. I would try another cable from a different manufacturer. Apple cables are expensive but they do work best.
 

gowanis

macrumors 6502
Original poster
Sep 22, 2007
413
7
What cable would you recommend? I called my local Apple store before buying my current cable, and they had nothing to offer that is direct USB-C to Displayport. Also, any comment on the brightness issue?
 

chscag

macrumors 601
Feb 17, 2008
4,622
1,946
Fort Worth, Texas
I just looked up the specs on your monitor at the LG web site. The brightness difference is a no brainer. Your iMac screen is 500 nits while the LG is only 300 nits. Also the LG has HDMI and Displayport connections. Where are you getting the USB-c from? Your iMac output connections are TB (Displayport).
 

chscag

macrumors 601
Feb 17, 2008
4,622
1,946
Fort Worth, Texas
I still don't understand the use of that cable. Displayport to HDMI would seem to be a better choice and in fact might work better. However, that's up to you.
 

gowanis

macrumors 6502
Original poster
Sep 22, 2007
413
7
Isn't is true that if you use HDMI, you can only get 30hz refresh instead of 60hz ?
 
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