Pattern to record: Power is present but the Mac remains black or repeatedly enters recovery behaviour.

Use the correct Mac power design

Identify the iMac before tracing power: the 24-inch Apple-silicon iMac uses its dedicated external adapter, while many earlier models take mains power into the chassis. Record whether the display, fans or other functions show any startup activity. Startup firmware is incomplete or corrupted and normal boot cannot begin.

Power and data precautions

The external adapter or internal mains supply can contain hazardous voltage; display removal requires trained handling. A restore can erase data, so the selected recovery action must be understood first.

Model-specific checks

1. Identify the external-adapter or internal-supply design, then distinguish startup activity from a built-in display or backlight fault.
2. Identify the Mac generation and follow its documented recovery procedure after confirming stable power; revive/restore procedures apply only to supported Apple-silicon or T2 models.

Repair and startup verification

If the checks support this cause, use the supported recovery action for that model, distinguishing a data-preserving revive from an erasing restore where those options exist. Verification should cover cold start, built-in display, brightness, processor load, sleep and restart.

Reference: Apple support guidance.

For an assessment of your iMac, contact AEPC in Burswood or call 027 908 8880. Provide the model and the conditions that reproduce this problem. Workshop visits are by appointment.