Is there a reset or fuse to restore power on a brother MFC-7820N

Yes, there is a fuse, two actually, inside the unit. My 7820N died after a power surge. here is how I fixed it.

unplug the power cord
raise the glass/ feeder assembly
open the front cover and remove the toner cartride.
Remove the phillips screw on the right side of the printer (same side as the power switch)
open the back paper path cover and remove the phillips screw
Flip the printer on its side and using a small screwdriver, press in the tabs that hold on the side cover. as with everything plastic, be careful since things break easily.

Once the side cover is off, remove the screws holding down the large metal cover over the power supply
Remove the screws holding the circuit board.
remove the three connectors on the front side of the board and flip it around.

By the time you have reached this point, you have probably noticed little pieces of fuse and MOV scattered around the inside of the unit, assuming you had a good power spike.

The fuse that blew for me as a 4 amp, fast blow fuse. It is soldered into the circuit board. I unsoldered the ends of the fuse that remained and soldered in a new 4 amp 5x20mm fast blow fuse. the MOV was also blasted, but I didn't have one of those to replace it and you can't get them at Radio Shack. I'll just plug it into a surge suppressor which will accomplish the same thing.

After reassembling, I was back in business.