iMac & Mac Desktop Won’t Turn On

On a desktop Mac, "will not turn on" splits into three very different repairs, and the price varies accordingly: the power supply, the logic board, or a display fault on a machine that is actually running fine. Working out which comes first, because replacing the wrong one is expensive and fixes nothing.

The iMac power supply is the most common single culprit on Intel machines, and it is also the most reassuring — it is a discrete part inside the chassis rather than a soldered section of the logic board, so replacing it is a contained job. Mac minis and Mac Studios use external or internal supplies depending on the model, and on those the fault more often sits on the board.

Before assuming the worst, two things are worth trying and cost nothing. Unplug the machine at the wall, leave it for a full minute and plug it back in — that drains residual charge and resolves a genuine share of no-power cases. And if the fans spin and it sounds alive but the screen is black, shine a torch at the display at an angle: a faint image means the machine is running and the fault is the backlight, which is a far smaller repair than anything on this page.

Where the board is genuinely at fault, this is microscope work rather than a board swap. We trace the power rails to find where the voltage stops and repair the specific component that has failed — usually a shorted capacitor or a failed power management chip, often the legacy of a power surge or years of heat. Replacing whole logic boards is the expensive answer most places give because component-level repair is not something they do. If your files matter, say so early: on any Mac with a soldered SSD the window to recover data is while the board can still be brought up.