The side key lock you refereed to is for the jackpot reset, and for getting into the book keeping. You should have a small circuit board mounted to the hopper. On that board you should see two red push buttons. One is for getting into test modes, the other is a reset switch.. From your one picture, it looks like the fuse block holder is hanging in the back.. I can't see the machines power supply, it should be mounted behind the hopper on the back wall. I would start by inspecting the power supply plug for burnt connections, then using a voltage meter check the voltages on the power supply.. There are 4 loops, one is ground, and the other three are voltages of 5V, 7.5V, and 10V... I can't read what numbers are in the win meter on the door.. You should also see a grey ribbon cable connecting the MPU board to the I/O board.. The pins on the ribbon plugs are easily damaged and broken off. If they become damaged, you will need to replace the ribbon cable..