Sorry, I've been without internet and power for a few days.. had an ice storm here in Michigan..
My AA does just fine with power outages. even after 12 hours with no power to the boiler, the fire is ready to go. It just takes a few minutes to get up to full heat.
Vampiro, you can Just keep the coal supply tube at the top of the transfer head full of coal. and hand ash every hour or two. you can run it without the auger turning. Might as well use the coal heat. The fire won't go out for more than a day or more.
Did you take the gearbox apart and look inside ?? sometimes the chain and sprockets are binding from worn teeth and stretched chains.
45* should work for the angle of the floor of the hopper. sorry, no line drawings of the hopper. It's just 4 2x4's in a square about 55", with a sloped floor. the hole in the bottom opens at the end of the auger. I can remove the side of the wood 'doghouse' to clean out the fines that accumulate. but the last few years, I just ran the coal all the way down, then used a small shovel to force the fines into the auger, and burnt them up. As long as the fines don't get wet and turn into black mud, they will feed into the auger with the coal, and burn with the coal.