20 - 30 Minuten
The issue I had is one of the most annoying. It started a 6 months ago with suddenly spinning hard-drive, blinking screen and often followed by a reboot, or sometime just reboots without a warning.
Problem was that my iMac (27inch mid-2011 3,4GHz) could run quite stable for a few days followed by days of frustration and an unworkable unstable system. Also the moment when the problems occurred was not clear.
I'd send the system to a Apple repair system, but they couldn't find an issue and returned with the solution " fixed error on filesystem". However I reinstalled already the full system without success.
Worked a few months with it again and tried to find the root cause.
The system was reasonable stable when running OSX from the build-in SSD drive. Reasonable means, almost no reboots but I still got the blinking screen and spinning HD. But running from bootcamp on the normal Hard drive was incredible unstable.
My conclusion was that the Hard drive was broken or a broken power supply which is dropping the power.
Power Supply made more sense to me and luckily I was right.
I was happy that I could get a power supply through iFixit since it is quite hard to get parts for an iMac.
iFixit thanks for the fast shipment, the PSU arrived 3 days later here in the Netherlands!
The repair went well and is much easier then adding an SSD drive in to it. I had the right tools since I also added before a SSD drive.
Took me a 20 minutes to get it done.
System runs now stable as it should be.
The iFixit manual says that you should first disconnect the cables and then lift-up the PSU. I would advice to first slightly lift-up the power supply. It will make it much easier to disconnect the cables.