For a fan to do the job there has to be a path coming in and a path going out. If the fan is setting inside the cabinet with the screen on the door it is moving the air around and not really pulling conditioned air thru the cabinet to remove the hot air. I am sure it works to a certain degree.
My equipment is in the center cabinet above the TV. I installed an axial fan in the divider on the left side sucking conditioned air thru the gap between the doors and the gaps around the edges between the doors and the cabinet face frame. I positioned the fan to suck air from equip cabinet and blow out thru gaps around the door on left cabinet.
I have the fan on a cooling stat so it does not run all the time, only when the temp rises to the setting on the stat.
I put spacer blocks under the Hopper with velcro.