Late 2015 27” iMac Recovery Mode NOT working

[PeacefulMan]

Hi, newbie to Macs and only used PCs,

I bought a late 2015 27” 5K iMac with removed internal disk, so no HDD/SSD. I’m planning to add an SSD but before that I tried to start it in Recovery Mode and I get nothing.

I started it while holding the “Option” key (tried also other combinations of keys: Command+R, Command+Option+R, Command+Shift+Option+R), I can hear the welcoming sound of the mac, but nothing happened on the screen and it stayed black/blank. I can just hear the fan speed ramping up to a max. I’m using a “wired” Apple keyboard (NOT wireless). I tried this many times and I stayed pushing on the keys over 2 minutes.

Maybe something wrong with the iMac? or whomever removed the internal disk did something wrong when they opened it? Maybe didn’t attach the screen cables back? I’m trying to diagnose it without opening it yet.

Is there a way to power the 2015 screen just to make sure they connected the internal cables, I mean using this 2015 as a second monitor or use it to display some pictures from a camera or a PC maybe?

FYI, I do have a second Late 2013 – 21.5” functional iMac if that can be used to power the 2015 monitor. Although I might not have adaptors and cables on hand.

This is the 2015 model I have:

https://everymac.com/systems/apple/...-inch-aluminum-retina-5k-late-2015-specs.html

Thank you!

PS1: I did buy an SSD blade and tried to make it an external boot disk (inside an enclosure) and it was very challenging. I think I might have succeeded, but when I plugged it to the 2015 it doesn't boot on it or do anything. That's a different topic, but now I would like to know why I can't get into recovery mode, my understanding is that I should be able to start the 2015 iMac by itself using some built-in Apple Bios startup in recovery mode without even having any internal disk?

PS2: I recall reading something about the fan speed issue if one of the cables inside is left in:

https://forums.macrumors.com/threads/late-2015-imac-27-upgrade-to-nvme-ssd-and-remove-stock-hdd.2247697/

 

[Nguyen Duc Hieu]

You need a working display to diagnose the iMac issue.
You can attach an external display using miniDisplayPort to HDMI or mDP to DP cable.
You can use a working Mac OS pre-install external disk (created on your iMac 2013, perhaps), instead of Internet Recorvery mode.

It's quite risky buying a second-hand electronic device without the chance to test its functionality.

 

[PeacefulMan]

You can use a working Mac OS pre-install external disk (created on your iMac 2013, perhaps), instead of Internet Recorvery mode.

We that part I struggled with it and it was the next post but before that I wanted to make sure the 2015 machine/screen is working first. I did make an external boot (I think) with the SSD blade inside an enclosure and plugged to the iMac and the same thing with a black screen.

You can attach an external display using miniDisplayPort to HDMI or mDP to DP cable.

I couldn't find that kind of cable at home, I found something that looks like an mDP x USB, I didn't even plug the square end to the mac to check, as the other end is not HDMI. I'll have to buy some adapters then. If I understand, I should run a cable from the 2015 to some other monitor, can I use somehow the 2013? or my Windows laptop (T440s ThinkPad)? or maybe simply the TV? would this last solution work?

 

[Nguyen Duc Hieu]

We that part I struggled with it and it was the next post but before that I wanted to make sure the 2015 machine/screen is working first. I did make an external boot (I think) with the SSD blade inside an enclosure and plugged to the iMac and the same thing with a black screen.


I couldn't find that kind of cable at home, I found something that looks like an mDP x USB, I didn't even plug the square end to the mac to check, as the other end is not HDMI. I'll have to buy some adapters then. If I understand, I should run a cable from the 2015 to some other monitor, can I use somehow the 2013? or my Windows laptop (T440s ThinkPad)? or maybe simply the TV? would this last solution work?

Try the cable miniDisplayPort to HDMI. It should work if your iMac works.
It's around 10$ plus shipping for a test. It's supposed to work on your iMac 2013, too.
Connection layout: IMac 2015/2013 (Thunderbolt 2 port) => miniDisplayPort to HDMI cable => HDMI in on TV.

Although the specs on iMac 2013 and 2015 is Thunderbolt 2. Those ports do output video signal through DisplayPort protocol. And DisplayPort can be converted to HDMI easily on a small chip within the cable.

Amazon Basics Mini DisplayPort Male to HDMI Male Cable, 1080p, Gold-Plated Plugs, 6 Foot, Black for Personal Computer

Amazon Basics Mini DisplayPort to HDMI Display Adapter Cable - 6 Feet

www.amazon.com

For the Internal LCD, you can be assured that either the LCD panel is not connected, or broken.
Otherwise, the screen should light up and display something when powered on.

Also, even if the LCD panel is working, you might have to expect some pinkish edge, which is a very common issue with iMac 2015.

 

[AL2TEACH]

I did buy an SSD blade and tried to make it an external boot disk

Going to assume the blade is the SSD/HD. Crazy question but was it formatted?

 

[PeacefulMan]

Going to assume the blade is the SSD/HD. Crazy question but was it formatted?

It was formatted many times and tried different formats. If I fix the screen issue then I will put a post here about what I did to the SSD blade (1TB NVMe WD SN770). I was using the 2013 to format it and make it a boot disk following 2 or 3 different methods. etc. But before that I thought I better check the 2015 if it's working on recovery mode.

 

[PeacefulMan]

Although the specs on iMac 2013 and 2015 is Thunderbolt 2. Those ports do output video signal through DisplayPort protocol. And DisplayPort can be converted to HDMI easily on a small chip within the cable.

Thanks for the link. Are these cables the same if I buy them from AliExpress? what other cables/adapters would be handy to have at home, knowing that I have a 2013 mac and a Windows PC (Lenovo T440s)?

For the Internal LCD, you can be assured that either the LCD panel is not connected, or broken.

Do you think I should take a chance and open the machine, at least to have a look if those 2 flat cables are connected from the screen to the inside guts? I recall seeing in many videos that they need to have the screen almost closed to be able to connect the plugs, very tiny space to work around. I already have on hand one seal kit but I will order a second one just in case.

 

[Nguyen Duc Hieu]

Thanks for the link. Are these cables the same if I buy them from AliExpress? what other cables/adapters would be handy to have at home, knowing that I have a 2013 mac and a Windows PC (Lenovo T440s)?


Do you think I should take a chance and open the machine, at least to have a look if those 2 flat cables are connected from the screen to the inside guts? I recall seeing in many videos that they need to have the screen almost closed to be able to connect the plugs, very tiny space to work around. I already have on hand one seal kit but I will order a second one just in case.

The cable is to test the machine while keeping the LCD panel untouched.
If you decide to open the iMac, maybe you don't need the cable at all.
For a temporary option, you don't need to use the iMac proprietary adhesive. Just use some broad tape to secure the LCD panel to the frame.
The best practice is to crack open the LCD panel with the iMac lying down face up, so you don't have to worry about it falling over and break, while still unknow about its original condition.
It's also advisable to use the secure tape and/or keep the iMac lying face-up for several days after you have fixed the LCD panel and sealed it, to give the adhesive some time to harden.

Many people forgot this, and the result was devastating. Their LCD panels fell out and broke.

 

[PeacefulMan]

Thanks for the reminder about the screen. I will try to open it and check the cables connections.

I read also that there is no easy way to make these 2015 models and after as a secondary monitor.

 

[Nguyen Duc Hieu]

Thanks for the reminder about the screen. I will try to open it and check the cables connections.

I read also that there is no easy way to make these 2015 models and after as a secondary monitor.

We can't say anything until you can confirm that the LCD panel is still in working condition and doesn't have the pinky edge.

Provided that, spending 250$ for a LCD driver kit is not very efficient for the old model 2015.

 

[PeacefulMan]

We can't say anything until you can confirm that the LCD panel is still in working condition and doesn't have the pinky edge.

Provided that, spending 250$ for a LCD driver kit is not very efficient for the old model 2015.

So I finally cracked open the screen and found the two cables disconnected. Connected them back on as good as I can and held the screen with painters tape around. I noticed one cable with the wider plug did not have a tab to lock it like I saw on repair videos. So not sure if it’s broken or something I can fix. Anyhow, after that I started the mac and now I could see the recovery mode etc. I had the external enclosed SSD plugged in one of the USB ports. I followed Apple instructions and somehow I ended up with Monterey running (it started first El Capitan). The machine is fast I would say even with being run on external drive. I took few pictures. I’ll see if there is a way to add them here.

The other thing is some shadows on the bottom edge of the screen!


https://support.apple.com/en-gb/guide/mac-help/mchl338cf9a8/mac

 

[Nguyen Duc Hieu]

So I finally cracked open the screen and found the two cables disconnected. Connected them back on as good as I can and held the screen with painters tape around. I noticed one cable with the wider plug did not have a tab to lock it like I saw on repair videos. So not sure if it’s broken or something I can fix. Anyhow, after that I started the mac and now I could see the recovery mode etc. I had the external enclosed SSD plugged in one of the USB ports. I followed Apple instructions and somehow I ended up with Monterey running (it started first El Capitan). The machine is fast I would say even with being run on external drive. I took few pictures. I’ll see if there is a way to add them here.

The other thing is some shadows on the bottom edge of the screen!

Great news that the LCD panel is working and doesn't have pinky edge.
Your iMac is also working fine as well.
Bad new is that it got dust intrusion problem, which is quite troublesome to remove.

Don't worry about the cable locking mechanism. As long as the LCD panel is working and you are not going to set your iMac on a bumpy road trip, it will be fine. You can secure it in place with Kapton tape, as well. Or you can buy a replacement cable (10~15$ perhaps) for aesthetic purpose.

 

[PeacefulMan]

Great news that the LCD panel is working and doesn't have pinky edge.
Your iMac is also working fine as well.
Bad new is that it got dust intrusion problem, which is quite troublesome to remove.

Don't worry about the cable locking mechanism. As long as the LCD panel is working and you are not going to set your iMac on a bumpy road trip, it will be fine. You can secure it in place with Kapton tape, as well. Or you can buy a replacement cable (10~15$ perhaps) for aesthetic purpose.

Here are pictures of how it looks like, I put the screen into different colors and it's the same thing showing up at the bottom.
Next pictures are from the inside. One side it shows the 2 cables that I connected and the other side it shows some loose cable and also some clip that they taped to the chassis, probably that's part of the locking tab?
Oh, and that fan noise it went away after connecting the cables, I don't hear it at all.

 

[Nguyen Duc Hieu]

Oh no, the LCD panel is not having dust intrusion problem.
This symptom is called theater light, a result of bad LED bulbs, or dislocation of the LED bars inside the LCD panel.
Or is it an issue with the LCD backlight power circuit or socket on the logicboard? I don't know.

Anyway, it's a hardware issue and you would need to disassemble the LCD panel to fix if necessary. Too troublesome and quite risky as hell.

I would just leave it there and focus on keeping the iMac running.

 

[PeacefulMan]

Oh no, the LCD panel is not having dust intrusion problem.
This symptom is called theater light, a result of bad LED bulbs, or dislocation of the LED bars inside the LCD panel.
Or is it an issue with the LCD backlight power circuit or socket on the logicboard? I don't know.

Anyway, it's a hardware issue and you would need to disassemble the LCD panel to fix if necessary. Too troublesome and quite risky as hell.

I would just leave it there and focus on keeping the iMac running.

That sounds complicated. I recall once fixing a TV that had some darkness or shadow in the screen. After researching all that, I bought online some LED backlights and disassembled it, put them in and it worked. But I don't think it's that easy with these computers. Regardless, I'll have to open it to install the SSD blade.