Remove the four screws on the top of the amp. These screws are significantly longer than the back panel screws.

Remove the quarter inch speaker cable from the jack in the back of the amp.

Unscrew the three remaining screws on the back side of the amp head as indicated by the red circles. Be sure to keep the amp secure as you do this because it will no longer be supported by any screws

Carefully remove the amplifier head from the speaker cabinet.

Refer to the guide on replacing the Power Tubes and Preamp Tubes to remove the tubes from the amp head. This is so you can safely set the amp head down without risking breaking a tube.