When the power button does not power on the system, you can try to run a magnetized/polarized screwdriver to jump the power pins directly on the motherboard.
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Step 2 - Access inside of the system and remove the ribbon cable from the motherboard's front panel jumper pins
If you are unsure how to remove the chassis lid to access the internal system hardware components, please visit Removing the Chassis Cover (TWS-1686525).
Step 3 - Run a magnetized/polarized screwdriver to jump the power pins directly on the motherboard
Below is an example of a set of front panel pins. It is usually at the end of the set of pins that has the PWR and its respective Ground pin.
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