The master port is the USB-C port next to the Ethernet Port. Connect the other end of the USB-C cable to the master port of your bricked iMac.Connect one end to any port of your host MacBook. Unplug the power cord of your bricked iMac.Open the app and make sure your host MacBook is connected to the internet. You may need to update to the latest macOS to run the app. Go to Apple’s website to download the app Apple Configurator 2.Then you force the bricked iMac into DFU mode so you can transfer the firmware to the bricked iMac via a USB-C cable. To fix a bricked iMac, you need a working host MacBook and download the firmware from Apple’s website. In other words, you may have bricked your iMac. If you updated your iMac’s macOS to one that contains a device firmware update (DFU) but failed to complete the whole process for some reason, you could end up with T2 chip firmware corruption. If the T2 chip is not functional, it won’t respond to the power button and your iMac won’t power on. Starting in 2018, Apple integrated the SMC chip to a larger multifunctional chip called Apple T2 security chip in the new Macs. You may need to repeat step 3 to step 5 for a few times.Keep pushing and releasing the button to get the dirt out of the button.Wait for a few minutes until the lubricant softens the dirt.Apply one or two drops of WD-40 lubricant to the button.Put the iMac on a flat desktop with the screen facing down.You can easily remove the dirt without replacing the button by following this procedure: Luckily, most of the time, a failed iMac power button is caused by dirt, not the electrical contact failure inside the power button. You need to remove the iMac screen, the power supply and logic board before you can get access to the power button. iMac power button replacement is a time-consuming task even for a Mac repair professional. The sticky power button is caused by the dirt accumulated inside the button. If you have a sticky power button or a faulty power button, the power button will not be able to send a valid control signal to the logic board so your iMac will not turn on.

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