Dickon Whitehead

Hi my iMac is stalling during the startup process. Using any of the following methods the result was the same: progress...

I'd strongly recommend buying the top case housing including the keyboard, fitting that is tough enough but much easier than replacing keyboard part on its own. Having done both!

is this an external keyboard or one in a laptop?

If you can test the drive in an external enclosure either as the startup drive for your mac or for another mac. This way you test the drive and check if its the ribbon cable (or something else like chip or component) at the same time. So if drive ok when booted external them its ribbon or another issue, if its not ok then most probably the drive! To boot from external drive hold down alt key immediately after pressing power button on the mac to boot it up.

No need to remove the screen or any cable except that which is directly connected to the home button!!! just prop it open the phone with screen facing up, an angle of about 45 to 60 degrees will give enough working space to remove and replace the home button.

The trickiest part is connecting the home button cable and getting its retaining clip in place.