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Manu182

macrumors newbie
Original poster
Feb 1, 2022
13
3
Hello all,

I have here a MacBookPro9,2 (Macbook Pro 13 Mid 2012) with the latest Monterey in version 12.6. Currently I have the problem that I get no signal on my external monitor via MiniDP. I have tested two different adapters. The integrated display goes black briefly and comes back again.

I have not used the Macbook on an external monitor for a very long time now. I upgraded it with 512GB SSD, 16GB RAM and WiFi BCM943602CS. Everything works great except the external display doesn't like it.

Processor is a 2.5 GHz dual-core Intel Core i5 and accordingly with the integrated GPU Intel HD Graphics 4000 1536 MB.

Additionally, a Windows 10 legacy is installed. Again, the external monitor does not work. I have done a PRAM and SMC reset.

Anyone else have any ideas? Is it because of OpenCore EFI? However, it only boots my macOS and not Windows.
 

Manu182

macrumors newbie
Original poster
Feb 1, 2022
13
3
Have you confirmed that both adapters and the monitor works with another mid 2012?
Yep, both working. Tried on an iMac 2011 with no issues.
Tried booting from an external drive with an OS supported by your Mac?
Good point!
I just tested a Catalina (last OS which is officially supported) again. Here I have the same problems. Display goes black briefly, but no signal on the external monitor. Now I'm a bit confused where the problem could be.
 
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Manu182

macrumors newbie
Original poster
Feb 1, 2022
13
3
The diagnosis only says that it cannot find wifi. It must be the wifi upgrade. Otherwise everything is OK.
 

Audit13

macrumors 604
Apr 19, 2017
6,781
1,798
Toronto, Ontario, Canada
Does the MacBook seem to boot to the desktop even though the display is blank?

Have you tried shining a bright light on the MacBook screen to see if there is anything visible? You could also try shining a light through the Apple logo at the top of the lid.
 

Manu182

macrumors newbie
Original poster
Feb 1, 2022
13
3
The MacBook display is totally fine. Everything is working perfectly, only this one issue with MiniDP. I have uploaded a Video where you can see that I connect the cable.

 

Manu182

macrumors newbie
Original poster
Feb 1, 2022
13
3
The port recognises something, otherwise the picture on the macbook would not briefly go black. But yes, in the meantime I also assume that it is defective. :(

Thank you very much for your support!
 
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Jesse_Bassett

macrumors member
Jan 29, 2021
30
12
Inver Grove Heights, MN
I know how to fix this! So if you open the bottom of the macbook up, there is a little switch on the bottom left side. It curves around and if it is bumped in anyway, the mac will not turn on. Make sure you reset this switch by unplugging it, then plugging it in. It will work! I have done this myself just recently.
 

Manu182

macrumors newbie
Original poster
Feb 1, 2022
13
3
I know how to fix this! So if you open the bottom of the macbook up, there is a little switch on the bottom left side. It curves around and if it is bumped in anyway, the mac will not turn on. Make sure you reset this switch by unplugging it, then plugging it in. It will work! I have done this myself just recently.
What for a switch do you mean? Do you have picture for example?
 

aijil

macrumors newbie
May 29, 2009
3
0
Couple of things to consider:
Try a different cable, or test your cable with another computer.
Try installing Windows via bootcamp and see if the port works in Windows

The port recognises something, otherwise the picture on the macbook would not briefly go black. But yes, in the meantime I also assume that it is defective. :(
Thank you very much for your support!
 

Manu182

macrumors newbie
Original poster
Feb 1, 2022
13
3
I buyer a used MacBook Pro 13 mid 2012 with i7 and only switched my harddisk to the new one. External Display now works as it should. So yes, it’s a hardware issue.
 

mintymiller

macrumors newbie
Oct 1, 2022
5
2
Leeds, UK
Hello all,

I have here a MacBookPro9,2 (Macbook Pro 13 Mid 2012) with the latest Monterey in version 12.6. Currently I have the problem that I get no signal on my external monitor via MiniDP. I have tested two different adapters. The integrated display goes black briefly and comes back again.

I have not used the Macbook on an external monitor for a very long time now. I upgraded it with 512GB SSD, 16GB RAM and WiFi BCM943602CS. Everything works great except the external display doesn't like it.

Processor is a 2.5 GHz dual-core Intel Core i5 and accordingly with the integrated GPU Intel HD Graphics 4000 1536 MB.

Additionally, a Windows 10 legacy is installed. Again, the external monitor does not work. I have done a PRAM and SMC reset.

Anyone else have any ideas? Is it because of OpenCore EFI? However, it only boots my macOS and not Windows.
I know it's been a while, but I've just seen this post after searching for a solution to exactly the same problem on my MBP 9,2! It's unlikely to be a hardware issue because my external display works fine when booting the MBP off an external HD running Mojave. I used Open Core 0.5.3 to upgrade to Monterey 12.6.2 and I think the subsequent display connection issue we both describe is caused by a sleep or monitor power down corrupting something in the video driver patch so that on wake, the external monitor is recognised (I can actually see it in the preference pane) but it won't display anything. I'm using an LG ultraHD external, which I have to admit is very fussy with connecting leads (in my case, a good quality miniDP to full DP cable). I can get the LG to display again after re-installing the Open Core patches (external disconnected) and rebooting the MBP and reconnecting. I'll check whether shutting down completely gets rid of the issue and if not, I'll try updating with patches from the most recent Open Core 0.6 update. Maybe that will fix it; I'll let you know.
 

mintymiller

macrumors newbie
Oct 1, 2022
5
2
Leeds, UK
Six months on, here's an update on my experience connecting and using a 24" LG 4K ultraHD display connected to my MBP 9,1 running the latest version of Monterey (Open Core EFI). This LG has two HDMI inputs and one (full size) displayport input. The old MBP has a single mini-displayport output that I believe is also Thunderbolt compatible. I have no issues whatsoever connecting via HDMI, but the best resolution I can get is standard HD at 1920 x 1080, which for a monitor capable of delivering a native 3840 x 2160 is inadequate to say the least. The HDMI is stable with the MBP in clamshell mode and the display always wakes from sleep without issue. Not such plain sailing with the LG's displayport input! My MBP has 1536 MB of dynamic video RAM, so should be able to drive the LG display at full res and when I get a connection, it does! I then scale back to 2560 x 1440 for best results. Getting a connection at all remains an issue. I connect the MBP and LG with an Ivanky miniDP to standardDP cable (a pretty good cable but not supported by LG who provide their own cables with the monitor; I would still need an adaptor to use their cable anyway) and booting the MBP will usually activate the external display. But this requires the MBP being at least slightly open and its display working (in secondary mode). In clamshell mode, it's just too hit and miss. And the best way to ensure the LG remains connected when I'm not working is to shut down and reboot the MBP when I need to. A bit inconvenient, but at least it reduces the carbon footprint! If I just log out, the LG will go into sleep mode (unavoidable) and the chances of my being able to wake it up again (by tapping the keyboard, for example) is about 70:30. When it won't wake, I'm better off just logging in (using the built-in display), shutting down and rebooting. Dsconnecting the LG's power cable for a few seconds before rebooting is recommended. Just disconnecting the DP cable usually doesn't help! So, the best I can do, is keep the MBP slightly open with the LG configured as the main display. I don't let the Mac or display sleep and I risk having to reboot after a log-out (which makes the LG sleep). I normally shut it down at the end of the day.

What have I learned from all this? Well, it's remarkable that a 10+ year old MBP can run a more recent UHD monitor at all, but it looks like there is no reliable fix for sleep/power-related disconnection problems and reading various forums, it continues to crop up with more recent Mac laptops, including those running on Apple silicon with more up-to-date interfaces like USB-C. A common feature of the complaints (including in my experience) is that the Mac thinks it's connected to the display on waking up, but actually isn't. If you look at displays preferences, both displays are active but the external is blank and in my case, sleeps (which the Mac doesn't acknowledge). Something's going on (and always has) with Apple's implementation of power management and video output on laptops that mishandles handshaking with some external displays I'm not expecting a a fix for this any time soon and will continue to muddle along until my old MBP fails and needs replacement or I just replace this rather nice LG display with an older but more supported model.
 

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