Connect AC power to PSUs 1 to 8. Once the FortiGate-7121F chassis is connected to power the chassis powers up. If the chassis is operating correctly, the LEDs on the PSUs and fans should be solid green. As well, the LEDs on the SMMs should be lit.
When the chassis first starts up you should also hear the cooling fans operating.
In addition, if any modules have been installed in the chassis they should power on and their front panel LEDs should indicate that they are starting up and operating normally.