Why would the fuse blow on the circuit board? I changed it last night at 6PM and 9:30AM it was out again could it be a capacitor?

If an onboard capacitor shorted, it could, you could disconnect all control wires, and see if it blows to determine if on board or thermostat and compressor control wiring, If it happens when set to cool it could be contactor control wiring. Tough to do since it takes hours to fail.
I would maybe visually check all low voltage wiring first.