It's probably the DC/DC board. The DC DC board is not at the bottom, it's at the top under the power button. Contrary to popular belief, the 7d is not weatherproofed AT ALL and moisture is able to squeak through the cracks in several places. I've replaced this board twice. If you decide to do it, it is not that hard but make sure you discharge the flash capacitor first (use a heavy duty resister NOT A SCREWDRIVER). Take a lot of pictures and use a cupcake pan to put the parts and screws. Sometimes when one of the other boards is bad, the DC board will go out again (it has fuses on it). The next logical one to replace is the flash capacitor board. Both are available cheaply.