Just install SSD now Mac not perfoming

[thewall]

After having the flashing ? on a 2015 27” with Fusion Drive I managed to get the old HD running ok on Mojave,so as I had the kit to put a SSD with Big Sur installed when I had the SSD as an external drive, everything went ok until I switched it on, it takes an age to load from start up or restart, and when I put it to sleep it won’t wake, also once passed the login screen the letters lopikjhm don’t work on the keyboard but they do on the login screen.

 

[bzgnyc2]

After having the flashing ? on a 2015 27” with Fusion Drive

Can you confirm whether this is the iMac15,1; iMac16,2; or iMac17,1?

I managed to get the old HD running ok on Mojave,so as I had the kit to put a SSD with Big Sur

If Big Sur, was it because you have the iMac15,1? Do you need Big Sur or could you go back to Catalina or Mojave?

installed when I had the SSD as an external drive, everything went ok until I switched it on, it takes an age to load from start up or restart,

Which model of SSD?

and when I put it to sleep it won’t wake, also once passed the login screen the letters lopikjhm don’t work on the keyboard but they do on the login screen.

This is of course all weird. I can't think of a single explanation that would explain all these issues. Few questions:
1) Could you have damaged the logic board or similar when swapping the devices?

2) Is the system workable enough that you could create another account or profile to test the keyboard after logging into that account?

3) Do you have another keyboard that you could try (with no explanation at the moment of why the keyboard would work on the login screen but not once logged in)?

4) Is it practical to wipe the now internal SSD and install a fresh copy of Mojave (or even Big Sur) onto it?

 

[thewall]

Can you confirm whether this is the iMac15,1; iMac16,2; or iMac17,1?

Late 2014 15,1

If Big Sur, was it because you have the iMac15,1? Do you need Big Sur or could you go back to Catalina or Mojave?

It was running Big Sur ok before the flashing ? might get away with Catalina as its my daughters and it needs to run Sims4

Which model of SSD?

Integral 500gb

This is of course all weird. I can't think of a single explanation that would explain all these issues. Few questions:
1) Could you have damaged the logic board or similar when swapping the devices?

I don’t see how only swapped HD

2) Is the system workable enough that you could create another account or profile to test the keyboard after logging into that account?

I will try this

3) Do you have another keyboard that you could try (with no explanation at the moment of why the keyboard would work on the login screen but not once logged in)?

Yes I do I will give it a go

4) Is it practical to wipe the now internal SSD and install a fresh copy of Mojave (or even Big Sur) onto it?

That was going to be my next step

Thanks for all the questions I want to get as much info before I try anything
I understand that there is a SSD of about 120gb installed somewhere could this be failing.
I started another thread a couple of months ago regarding the same iMac which will explain what I have done.
When I had the original HD in I couldn’t install BigSur it just would not install it on a clean install, had Mojave running great before she took it away and tried to install Big Sur then it went pear shape again, can’t understand why it won’t load BS when before it went wrong it was running it ok

 

[bzgnyc2]

Late 2014 15,1

It was running Big Sur ok before the flashing ? might get away with Catalina as its my daughters and it needs to run Sims4

I am familiar with that need...

Integral 500gb

Don't know that particular SSD and will just say not my first choice for a boot drive for a Mac. If macOS doesn't like it's TRIM implementation (an issue with other SSD), that could explain the long boot times.

FYI in case anyone has experience with these drives:
Lexar NM710
Lexar NQ790

The Integral 500GB appears to be a copy of them as per https://www.techpowerup.com/ssd-specs/integral-m3-plus-500-gb.d2472

I don’t see how only swapped HD

Just wanted to get your sense since wasn't sure how much you moved stuff around and your sense of how surgical you were with the procedure.

Just a sanity check, have you tried running the extended Apple Diagnostics?

Use Apple Diagnostics to test your Mac - Apple Support

Apple Diagnostics, formerly known as Apple Hardware Test, can check your Mac for hardware issues.

support.apple.com

I understand that there is a SSD of about 120gb installed somewhere could this be failing.

Not quite sure I follow this -- are you saying you left the 120GB SSD associated with the Fusion drive in there? If so that is something I would try to remove given these are known to fail after 10 years (and if failing, unclear how the system would react to it). I say this not knowing how hard it is to remove such from that model of iMac (I've heard this can be quite an ordeal on some models of iMac).

 

[thewall]

Thanks for the info
All I’ve done is watch vids on YT and never seen anybody replace the SSD when replacing the HD
The SSD i installed was not the most expensive so it might be coming back on me now
Will try the hardware test
Might go down the route of doing a reinstall upto Catalina see how it starts up, have seen vids on how to get Fusion Drive up and running, but was told that with a SSD I wouldn’t need the Fusion Drive weather this is right I wouldn’t know , was just so pleased to get the screen of without breaking it

 

[thewall]

Ok today I reset the SMC/NVRAM and now everything is working ok did the apple hardware diagnostics and it passed with no problems, regardless the keyboard I had switched on the mouse keys which disabled those particular keys, so at the moment i happy