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Dual Display rebooting issue

I just setup a new MacBook Pro Core I7 mid 2015 (DG) . Previously the user had a The Mac Pro "Quad Core" 2.8 (Mid-2010/Nehalem). they were using two different screens One NEC LDD2690WuXi2 and a NEC MultiSync PA271W. they were working fine . The new configuration is setup like this >

Monitors are connected via thunderbolt ports one monitor is connected directly

and the other is connected to the thunder bolt docking station

the issue is this

if you restart the machine. the screens go blank and never come on . the right

screen shows a signal comming into it but nothing is displayed. the only way to

get it to display again is to hold down the power button in as if you were

forcing a shutdown.

this occurs almost everytime with the laptop lid closed . If you try to reboot

with the lid open it reacts differently ( screens come back on . this is not consistent) Below are the steps I used to trouble shoot and isolate the issue .

If anyone has any other suggestions or want to use this as a trouble shooting reference then  please do.

Disconnected Everything from the LT and Restarted shut down several

times - no issues

connected both monitors  Directly to Thunderbolt port. with lid

open machine seems to reboot just fine and displays come back up

Closed lid

and restarted, monitors do not come back on.

Tried it a second time , same

issue . You can hear the fans spinning in the machine. At this point you need to

do a cold boot .

checked crash logs events etc for any detail . none to be

found.

Every once in a while the machine will reboot With the lid closed ,

but most of the time it does not .

Noticed that the WiFi has turned its

self  off for some reason , tried the rebooting sequences  with both monitors

connected and the lid closed and open with also toggle the wifi on and off

before restarting and when the WiFi is off it seems to be better .

Disconnected the right monitor and connected the left monitor to the front

thunderbolt port and re tried operations . machine restarted

successfully

Tried the same operation with the left monitor plugged into the

rear thunderbolt port . Machine restarts successfully.

Tried the same

operation with the External thunderbolt docking station plugged into the rear

TB port and the left monitor in the front TB port and rebooting was

successful

swapped the ports around and also rebooting was successful .

Tried all the same test with the right Monitor and the problem is back .

noticed that if you open the screen and pull the thunderbolt cable from the

machine you now see video on the Laptop screen

The machine also has a HDMI port . tried hooking up the right monitor to this

port  do all the same operations and there is no video on screen .

One of

the other users has a very similar mac. the only real difference is this mac

has a higher end video card  AMD Radeon R9 M370X 2048 MB . With both monitors

hooked up in the original configuration the test computer displays video every

time .

Hooked up two Dell Monitors to the original machine in the original

configuration  and the displays work perfectly . Rebooting shows displays every

time ./

Will let the user know that they can either deal with the issue

or we will purchase new monitors . we need to do research on which one to buy ,

but it looks like the Dell Ultra sharp ones should do the trick .

which cables do I need to connect my dell laptop to mac thunder bolt monitor

最后更新：2017-08-18 01:11:59

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