637      iPhone_iPad_Mac_apple

My iMac had been turned off during an update...

Shut down

Disconnect all external devices except OEM mouse, keyboard

reset the smc

https://support.apple.com/en-us/HT201295

reset the NVRAM

How to reset NVRAM on your Mac - Apple Support

then boot into safe mode

https://support.apple.com/en-us/HT201262

then reboot normally with devices disconnected.

if you are unable to reboot to the OS see this article on reinstalling or restoring (provided you had a Time Machine Backup) your Mac:

About macOS Recovery - Apple Support

But theirs nothing displaying...

Do the resets that were suggested, you don't need to have anything displaying to execute them.

It's currently in a repair shop and their saying that these resets aren't currently working :/

Do you have a firmware password enabled on that system?

that would prevent recovery

I tend not to mess with that stuff. It's all factory default currently :/ is their a potential hardware failure? Maybe PSU? Or because the OS has corrupted, could it be that? And that pic is from the last time I managed to get it on which was once in a blue moon. :/

it appears to be software but I'm not licensed to make that call with 100% guarantee.

I would try an internet recovery restore if you have run out of options.

About macOS Recovery - Apple Support

I believe it too be a software company issue... would replacing the HDD with one with a copy of the OS rule that out or in do you reckon?

最后更新：2017-10-16 23:34:59

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