It shutdown and never came back
As I was working on my Mid 2010 27” iMac, the screen changed with strange graphic artifacts. I shut it down and after a min when I tried to power it back on again it just wouldn’t start.
When I pressed the power button I could hear the fans starting to work but after 5secs they stoped. No chime was heard, nor would the iMac boot. Screen remained black.
I was working with High Sierra. Maybe I’m lucky that I got a TimeMachine backup, but I have no clue what my next step can be… I’m totally lost ?
PS: Supposedly if I buy a new, up to date iMac, can I use the TimeMachine backup I have from High Sierra system to restore my old iMac stuff on the new system?
Update (09/06/2021)
I did a few things: Removed the Display and GPU (Didn't remove the GPU temp sensor)
- Did a PRAM reset
- Fans worked at high speed
- Heard the Chime once
Then I placed the GPU back and at boot there was a continuous chime. Strange because if its the GPU causing the continuous chime, why wasn't it there in the first place, before I opened the iMac and before I removed/connected the GPU?
Questa è una buona domanda?
5 Commenti
That still makes sense! Once your system fails it will set a latch to prevent you from restarting as SMC will prevent it. Once you disconnect the power cord and break the connections to SMC. SMC will reset which is why your system now has a different reaction.
Time for a new GPU board. Make sure you get a real Apple unit as they have custom firmware on them,
da Dan
Thanks so much Dan... just a few unknown words... latch? SMC?
da genik
Latch - A logic toggle state, in binary we talk about 0 - Off/1 On states which is how computers work! Here like HDD/SSD's a state is stored, here this state is held in a small area of SRAM in the SMC chip.
SMC - System Management Controller; The chip which takes care of all of the power & thermal aspects of the system to make sure everything is working correctly.
da Dan
@danj
Also, is there some way i can double check that a new GPU board is needed? Or is this a clear cut case? And if i find a new GPU how can i know its a real Apple unit? Some specific code to look for? Or some link for purchase u have in mind so i can see the specs perhaps?
Once I get a new graphics card and I install it, will the continuous chime sound stop, or must I do something specific for it?
da genik
@genik - Other than replacing it there is no means to check it. You might be able to check your system by using a USB wired keyboard forcing the system into Target Disk Mode. This bypasses the last part of POST using the systems BIOS (EFI) to boot up under, here you will see an icon on your display as the internal graphics engine in the CPU will be active. IF that works then you know it's the GPU board, but often the GPU board failure can be in a state that prevents Target Disk Mode so don't depend on it as an absolute.
Restart your system and press the T key to enter
Reference: Mac startup key combinations
Here's one source that offers the needed part 27" iMac AMD (ATI) Radeon HD 5670 or Radeon HD 5750 GPU boards
da Dan