Blank screen in any startup mode, hardware probably ok, but how do I access the software for a reset?

Frog224 wrote:

Hi, I have a tricky situation I don't really know how to get out of. I have an iMac 27" (2011, i5 3.1, 4 Gb RAM, High Sierra). ...... and it began to flicker. And then the screen went white. So I went through the standard procedures:

> Tried recovery mode (cmd-R): depending on its mood: end up with a blue striped screen

or a black screen

Sounds like a GPU failure.....some of the GPUs for the 27" 2011 iMac were known to fail and Apple even had a free repair program at one time (now long expired). The Apple Diagnostics may not always detect the failures.

> Tried normal startup: Apple appears, timer turns, then white screen

> Tried safe mode (shift): Apple appears, time bar runs to 1/3rd, then white screen

> Tried startup in hard disc mode (T): The screen displays the connection sign, but I

can't find the iMac's hard disc when connected to either of my macbook pro

(intel mid 2015 and M1 2020).

While these symptoms can also be related to a GPU failure, they also could be due to a Hard Drive failure. Unfortunately the Apple Diagnostics don't usually detect most drive failures.

You can try creating a bootable Knoppix USB stick in order to check the health of the internal Hard Drive. Post the full GSmartControl health report here so I can examine it. See my other post here with instructions for creating & using a bootable Knoppix USB stick to check the health of the internal Hard Drive......it is also a good way to see if Knoppix encounters any issues booting including graphical issues.

Creating a bootable Knoppix USB Stick to Check Health of Internal Hard Drive -- HWTech - Apple Community

> Tried Protocolstartup (cmd-v): runs nicely the protocol. But as I have no idea what to look

for I don't know if anything is missing.

If the system stalls or freezes while the boot log is still displayed on the screen, then you just look to see if any errors are listed, otherwise you look to see at what step the boot process got stuck to gather a clue. It is possible the step it got stuck on is the next step which never displayed on the screen. In that case it helps to know what is most likely to occur next.

So overall I am tempted to think that there is nothing wrong with the hardware. But I

don't know how to get onto the software. I am also wondering if I might have a

virus (with the recent short-notice shut-down of all early ESET software, there

is no ESET antivirus for this iOS anymore). I tried to use my other laptop with

up-to-date Antivirus to scan my iMac. But as it doesn't connect in hard disc

mode ...

There is no need for any anti-virus software, cleaning/optimizer apps, or third party security software on a Mac. These types of apps usually cause more problems than they solve because they interfere with the normal operation of macOS.