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Black screen and no boot up after trying to upgrade RAM on iMac 27" 2020

L

lovecd

macrumors regular
Original poster
Aug 14, 2022
165
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Trying to upgrade ram from factory 8GB to 32GB (4x8GB), but no image (can hear the fan spinning, but no chime sound, nothing else), put the old ram back, and still the samething (no image, nothing except the fan spinning), and no image on external monitor either. Removed all rams and turn it on (same thing, no beep, nothing but fan spinning). I don't think I damaged anything as I did the ram upgrade on my other iMac desktops many times before. So, what could be wrong here? Any thoughts?

Thanks,
 
I find the 2020 iMacs are a bit tough to get ram reading the first time even if it seems seated correctly - try putting one stick in and turning it on, and repeat the process for the other sticks
 
When you change RAM on the 2020 iMac it takes about an extra 30 seconds to boot, during which time there is a completely black screen and no sound, other than the fan. You have to be patient for up to a minute, or typically what happens is you try turning it on again which actually turns it off, then you get confused whether it is on or off.
 
TwoH said:
I find the 2020 iMacs are a bit tough to get ram reading the first time even if it seems seated correctly - try putting one stick in and turning it on, and repeat the process for the other sticks
Click to expand...
Already tried, but no luck.
 
wilberforce said:
When you change RAM on the 2020 iMac it takes about an extra 30 seconds to boot, during which time there is a completely black screen and no sound, other than the fan. You have to be patient for up to a minute, or typically what happens is you try turning it on again which actually turns it off, then you get confused whether it is on or off.
Click to expand...
I actually waited for about 5 min, but no luck.
 
I would suspect the power supply has failed.
If that doesn't help, then it will be the logic board.
(I think just a coincidence that something failed at the same time as your RAM upgrade)

But, first, I would try replacing the battery. (the button battery on the back side of the logic board.)
None of those steps are simple or quick.
Take your time, and follow a good repair guide. iFixit.com is pretty good at that (IMHO)
I would suggest that you fully test the iMac after any replacement, without "re-taping" the display.
My real recommendation, however, is to take to an Apple store to diagnose the problem. They should be able to swap out parts until the iMac boots again. (Unless you happen to stock replacement parts for any Mac that you own :D )
 
Wayyy before trying that I would try to do a restore via Apple configurator
 
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DeltaMac said:
I would suspect the power supply has failed.
If that doesn't help, then it will be the logic board.
(I think just a coincidence that something failed at the same time as your RAM upgrade)

But, first, I would try replacing the battery. (the button battery on the back side of the logic board.)
None of those steps are simple or quick.
Take your time, and follow a good repair guide. iFixit.com is pretty good at that (IMHO)
I would suggest that you fully test the iMac after any replacement, without "re-taping" the display.
My real recommendation, however, is to take to an Apple store to diagnose the problem. They should be able to swap out parts until the iMac boots again. (Unless you happen to stock replacement parts for any Mac that you own :D )
Click to expand...
Thanks a lot, will try it soon.
 
lovecd said:
What is Apple Configurator?
Click to expand...
Apple Configurator is an app that provides several methods to setup your Mac with, well, configurations.
Also, If you search for your issue (something like "Mac won't boot, black screen, fan runs, but no boot chime"), you will see some info about using the Configurator app to restore your Mac's firmware, very relevant with a 2020 iMac, which has the T2 chip. The Configurator app can restore/update the firmware in the chip. Could easily help you back to running. At least, it will be easier than taking your iMac apart to do what I mentioned above. You can download the Configurator app from your App Store.
Note: You will quickly find out that you need a second Mac to do a restore using Configurator. Both Macs must be connected together before you can try a restore.
 
DeltaMac said:
Apple Configurator is an app that provides several methods to setup your Mac with, well, configurations.
Also, If you search for your issue (something like "Mac won't boot, black screen, fan runs, but no boot chime"), you will see some info about using the Configurator app to restore your Mac's firmware, very relevant with a 2020 iMac, which has the T2 chip. The Configurator app can restore/update the firmware in the chip. Could easily help you back to running. At least, it will be easier than taking your iMac apart to do what I mentioned above. You can download the Configurator app from your App Store.
Note: You will quickly find out that you need a second Mac to do a restore using Configurator. Both Macs must be connected together before you can try a restore.
Click to expand...
Thanks for telling me this, will do some home work tonight. By the way, when you said needing a second mac, does it mean it can be other forms of device like MacBook Pro laptop?
 
Might also want to keep trying with the old RAM, since it was confirmed working before. It can be tricky to seat it properly, I had to try a couple times myself with one of my many iMacs before it would boot up. If it still doesn't work after several tries, then try the software diagnostics mentioned above.
 
lovecd said:
Trying to upgrade ram from factory 8GB to 32GB (4x8GB), but no image (can hear the fan spinning, but no chime sound, nothing else), put the old ram back, and still the samething (no image, nothing except the fan spinning), and no image on external monitor either. Removed all rams and turn it on (same thing, no beep, nothing but fan spinning). I don't think I damaged anything as I did the ram upgrade on my other iMac desktops many times before. So, what could be wrong here? Any thoughts?

Thanks,
Click to expand...
1. Take the ram out and clean the insert with compressed air. Reinsert and make sure it it set in all the way.

2. Restart doing a PR ram reset cmd+option+P+R.

3. If that doesn’t work, you’re out of luck. Could be the ram you bought has an issue or it could be something else.
 
Timpetus said:
Might also want to keep trying with the old RAM, since it was confirmed working before. It can be tricky to seat it properly, I had to try a couple times myself with one of my many iMacs before it would boot up. If it still doesn't work after several tries, then try the software diagnostics mentioned above.
Click to expand...
Sure, thanks.
 
Hello All, here is the update:

I cleaned all ram slots with blower and tried different variations and it finally booting up now with either factory ram or upgraded chips, works great. thanks so much for all of your help!!!
 
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A bit late but I always make sure to use the same brand, same MHz/megatransfer, same amount of RAM when I upgrade the memory of my computer...

Mixing and matching is one of the reasons a computer receives power but does not boot... Removing and re-seating of memory module also helps...

It's good that it is now working for you...
 
winxmac said:
A bit late but I always make sure to use the same brand, same MHz/megatransfer, same amount of RAM when I upgrade the memory of my computer...

Mixing and matching is one of the reasons a computer receives power but does not boot... Removing and re-seating of memory module also helps...

It's good that it is now working for you...
Click to expand...
Yes, I always use same brand and same part number for all slots. And thanks for pointing this out!
 
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