Help can’t erase

[bear100]

Please help, I have a 28” late 2015. iMac Intel-based, I have been advised to buy a Samsung T7 SSD and use that as the bootable disc because the fusion part of my drive has failed, I have started the iMac in Internet recovery mode to a erase the macOS-based system and Apple HDD, but the erase button is greyed out? I have then tried to reinstall macOS Montery in recovery mode but option to select where to install has no options? I believe the USB is not working due to the failed part of my fusion drive. What can I do?

 

[rm5]

The SSD isn't even showing up in the list, or even as a device. That means that it's not detected or connected properly. Did you connect your T7 SSD? If so, it should be showing up there. Also, if the fusion drive is failing, why would you try to install macOS on it?

 

[DeltaMac]

Your Disk Utility screen shows a disk image, and nothing else. The image is not local to you, just what You iMac is using for booting to internet recovery. It's actually located on an Apple remote server, and you can't do anything with it, other than booting.
Click on the View icon, and make sure that "Show All Devices" is selected, or go to the View menu, where you can find the same choice to show all devices. That might make your internal drive show up in the list.
The fusion drive is actually two physical devices. A spinning hard drive (HDD), and an m.2-type card SSD. If your fusion drive was still functional, the two devices are combined by software into one virtual drive - that's your fusion drive.

 

[bear100]

The SSD isn't even showing up in the list, or even as a device. That means that it's not detected or connected properly. Did you connect your T7 SSD? If so, it should be showing up there. Also, if the fusion drive is failing, why would you try to install macOS on it?

Yes the T7 is connected but for some reason the usb connections are seen in terminal and have power but not used software wise, I want to us the T7 as the bootable (what has been suggested on another post)

 

[bear100]

Your Disk Utility screen shows a disk image, and nothing else. The image is not local to you, just what You iMac is using for booting to internet recovery. It's actually located on an Apple remote server, and you can't do anything with it, other than booting.
Click on the View icon, and make sure that "Show All Devices" is selected, or go to the View menu, where you can find the same choice to show all devices. That might make your internal drive show up in the list.
The fusion drive is actually two physical devices. A spinning hard drive (HDD), and an m.2-type card SSD. If your fusion drive was still functional, the two devices are combined by software into one virtual drive - that's your fusion drive.

Yeah I have selected View all devises and that is what it shows in the picture, not sure how move on from here? The Mac works but is very slow and I would like to revive it if at all possible

 

[DeltaMac]

Try going into your terminal, then type the command diskutil list
That command should list all the storage that is connected to your iMac. You would be looking for anything in that list that shows as an internal device.
If nothing internal appears with that command, then possibly you would want to disconnect the hard drive, as a minimum. That may have failed, and is now causing problems on the SATA bus.

 

[bear100]

Try going into your terminal, then type the command diskutil list
That command should list all the storage that is connected to your iMac. You would be looking for anything in that list that shows as an internal device.
If nothing internal appears with that command, then possibly you would want to disconnect the hard drive, as a minimum. That may have failed, and is now causing problems on the SATA bus.

Hi, this is what it shows does it look right?

 

[DeltaMac]

Yes, that is close to what I expected. You have a 2TB drive. And, that would be (only) the hard drive. The SSD is not showing at all.
The hard drive's name is IMAC.
It does not show up in Disk Utility, as you know now.
And, without the "help" from an SSD with the fusion drive, the spinning hard drive will often be quite slow. The only thing that helps now is the 27-inch iMac has a 7200 rpm hard drive, better than the 5400 rpm HDD that was standard in a 21.5-inch model at that time.
So, you don't have a fusion drive now. If you should have a fusion drive, you are now missing the SSD drive.
The SSD blade drive apparently has failed. You CAN replace that, but it's not an easy job.

 

[bear100]

Yes, that is close to what I expected. You have a 2TB drive. And, that would be (only) the hard drive. The SSD is not showing at all.
The hard drive's name is IMAC.
It does not show up in Disk Utility, as you know now.
And, without the "help" from an SSD with the fusion drive, the spinning hard drive will often be quite slow. The only thing that helps now is the 27-inch iMac has a 7200 rpm hard drive, better than the 5400 rpm HDD that was standard in a 21.5-inch model at that time.
So, you don't have a fusion drive now. If you should have a fusion drive, you are now missing the SSD drive.
The SSD blade drive apparently has failed. You CAN replace that, but it's not an easy job.

am i right in saying the SSD has the USB ports connected to it? if so (my USB's have failed recognising everything) its the reason they don't work. just googled the process and it very involved but to say the least but not out of my capabilities!! (hopefully) i don't have much choice anyway!. The T7 was never going to work with the failed USB sockets.
Ok so I'm going to give the SSD replacement a try what should i buy? sorry I'm a gas man and and get confused with tony stark talk! lol

 

[Fishrrman]

BEFORE GOING FUTHER, do you have (or NOT have) the t7 drive yet?
You NEED IT in your hands before trying to revive the iMac.

The USB ports will still be operative if the internal drive(s) fail.

Once you have the external SSD:
Go back and reboot into INTERNET recovery:
Command-OPTION-R
at boot.

Once the utilities load, connect your external USB3 SSD.

Open disk utility.
Go to the view menu and choose "show all devices".

Now look at the list on the left.

From the top down, you should see at least the internal HDD (even if the internal SSD is dead).
IGNORE THAT for now.

Underneath that, you should see the t7 drive (may not be formatted yet).
IF you can see the t7, click on it and erase it to "APFS, GUID partition format".

Once it's erased, quit disk utility and open the OS installer.
Start clicking through.
IMPORTANT: when the installer asks WHERE you want to install, make sure you select the t7 SSD.

The iMac will reboot one or more times, and the screen will go dark for a minute or more with no other indication of activity. Be patient.

When done, you should see the initial setup screen (choose your language).
At this point, either have a backup ready from which to restore when requested by setup assistant, or create a brand-new account "from scratch" and proceed from there.

 

[DeltaMac]

In answer to your question about SSD, and USB connections.
The SSD that I was talking about in the above post is the internal one, It does not have any kind of USB connection, but plugs in to a socket. It's a small circuit card, and the socket is a PCIe connector, The connection is much faster than the USB connection where you would plug in an external USB device.
Neither the HDD, nor the internal SSD have any relation to the USB bus.
But, even so, if you now realize that the USB connections seem to be lost, or simply intermittently working, then that may mean that part of the chipset -- those parts on the logic board (on a PC, usually called the motherboard) that control the CPU, also the graphics chip, makes the memory work, and controls everything that is connected in the computer. If you have problems with some of the connected devices, and the control chips are not working properly, then you may have problems with other kinds of connections on your computer. So, if you are having some connection weirdness, it may be the control chips on the logic board, and maybe that logic board is simply on its way out.

 

[bear100]

BEFORE GOING FUTHER, do you have (or NOT have) the t7 drive yet?
You NEED IT in your hands before trying to revive the iMac.

The USB ports will still be operative if the internal drive(s) fail.

Once you have the external SSD:
Go back and reboot into INTERNET recovery:
Command-OPTION-R
at boot.

Once the utilities load, connect your external USB3 SSD.

Open disk utility.
Go to the view menu and choose "show all devices".

Now look at the list on the left.

From the top down, you should see at least the internal HDD (even if the internal SSD is dead).
IGNORE THAT for now.

Underneath that, you should see the t7 drive (may not be formatted yet).
IF you can see the t7, click on it and erase it to "APFS, GUID partition format".

Once it's erased, quit disk utility and open the OS installer.
Start clicking through.
IMPORTANT: when the installer asks WHERE you want to install, make sure you select the t7 SSD.

The iMac will reboot one or more times, and the screen will go dark for a minute or more with no other indication of activity. Be patient.

When done, you should see the initial setup screen (choose your language).
At this point, either have a backup ready from which to restore when requested by setup assistant, or create a brand-new account "from scratch" and proceed from there.

Hi, yes Samsung 2TB T7 Shield SSD in hand, plug into USB it lights up for a few seconds and goes out, in disk utility nothing shows. I have been in Terminal and it sees the device and recognises it but for some reason the software bit doesn’t engage?
This is what I have and the T7 is plugged in.
I will follow your procedure after work today because the recovery mode takes about 20mins to load.

 

[bear100]

In answer to your question about SSD, and USB connections.
The SSD that I was talking about in the above post is the internal one, It does not have any kind of USB connection, but plugs in to a socket. It's a small circuit card, and the socket is a PCIe connector, The connection is much faster than the USB connection where you would plug in an external USB device.
Neither the HDD, nor the internal SSD have any relation to the USB bus.
But, even so, if you now realize that the USB connections seem to be lost, or simply intermittently working, then that may mean that part of the chipset -- those parts on the logic board (on a PC, usually called the motherboard) that control the CPU, also the graphics chip, makes the memory work, and controls everything that is connected in the computer. If you have problems with some of the connected devices, and the control chips are not working properly, then you may have problems with other kinds of connections on your computer. So, if you are having some connection weirdness, it may be the control chips on the logic board, and maybe that logic board is simply on its way out.

Thanks, I do get what you’re saying, the video I watched looked like the USBs were on or plugged into the SSD which made me think that’s why mine may be faulty. The USB ports all have power and are recognised in terminal but not in disk utility and don't the software side does nothing

 

[DeltaMac]

When you have the T7 plugged in to your iMac, run that diskutil list command in the terminal.
Does the T7 show up at all in the response to that command?

 

[Fishrrman]

Re post 12 above:
"This is what I have and the T7 is plugged in."

I suggest you try A DIFFERENT CONNECTING CABLE.

Also -- this may sound ridiculous, but unplug the USBc cable end from the t7, "turn it over" and plug it back in.

Do you have another Mac with which you can try the t7?
If not, do you have access to a PC on which you can try the t7?

 

[bear100]

When you have the T7 plugged in to your iMac, run that diskutil list command in the terminal.
Does the T7 show up at all in the response to that command?

yes it shows in terminal, bottom line

 

[bear100]

Re post 12 above:
"This is what I have and the T7 is plugged in."

I suggest you try A DIFFERENT CONNECTING CABLE.

Also -- this may sound ridiculous, but unplug the USBc cable end from the t7, "turn it over" and plug it back in.

Do you have another Mac with which you can try the t7?
If not, do you have access to a PC on which you can try the t7?

i am 100% positive the leads are working, as shown above terminal sees it but thetas as far as i can get. no other devices work either, eg flash pen, tomtom etc there is power so can charge my phone etc

 

[bear100]

Maybe i should try a thunderbolt to USB lead? if theres such a thing?

 

[DeltaMac]

If the USB ports don't pass any data, then that should also mean that a wired/USB keyboard or mouse will not work at all. Have you tried that?
Tried all 4 USB ports?

 

[bear100]

If the USB ports don't pass any data, then that should also mean that a wired/USB keyboard or mouse will not work at all. Have you tried that?
Tried all 4 USB ports?

tried all 4 ports but not the 2 thunderbolt ports, all of them power devices but still no data transfer. going to borrow a wired keyboard today to test 🤞

 

[bear100]

is there such a thing as a thunderbolt 2 to USB adapter? struggling to find something

 

[Fishrrman]

"is there such a thing as a thunderbolt 2 to USB adapter? struggling to find something"

A company called "Kanex" (I think that's the name) used to sell one, but that was some time ago (years).

You might be able to find a used one one ebay. May be priced too high. May work, or not work.

Why would anyone NEED a tbolt2-to-USB adapter?
If the drive is USB, plug it into a USB port.
If the drive is tbolt2, the adapter doesn't work anyway (it only works "one way", to connect a USB device to a tbolt port).

 

[DeltaMac]

Did you try a wired USB keyboard (or just a wired mouse), just to see if THAT works (showing that the USB ports are working for I/O devices)

 

[bear100]

"is there such a thing as a thunderbolt 2 to USB adapter? struggling to find something"

A company called "Kanex" (I think that's the name) used to sell one, but that was some time ago (years).

You might be able to find a used one one ebay. May be priced too high. May work, or not work.

Why would anyone NEED a tbolt2-to-USB adapter?
If the drive is USB, plug it into a USB port.
If the drive is tbolt2, the adapter doesn't work anyway (it only works "one way", to connect a USB device to a tbolt port).

yes i want to try one, my USB sockets have failed reading data and i need to plug in an external SSD so my thought was to try the thunderbolt ports in hope they would work.

 

[bear100]

Did you try a wired USB keyboard (or just a wired mouse), just to see if THAT works (showing that the USB ports are working for I/O devices)

my mate with the keyboard didn't show up, i will grab a wired mouse today and give it a try 👍