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I have had an Alpenrost (actually on my third) for over a year and have
logged about 120 roasts. The first unit melted during the first use:
apparently the fan didn't work. The second died suddenly during roast #83
and the third is fine. The roasting profile of the two usable units is
slightly different; the first was faster than the second. Therefore It
appears my "numbers" won't work for your machine exactly. I can say I have
never seen 5 min. to first crack though; my usual is in the 14 min. +/-
range (except decaf). I can say voltage seems to be important as I once used
it outside on the screen porch on a heavily loaded circuit and the roast was
completely off (much slower). I had always used and now always use a
dedicated circuit near my cooktop that has a good 120VAC reading +/-. Since
you are getting such widely varying roasts, I would check the voltage on the
circuit you are using to see where you stand or at least use the same outlet
all the time and nothing else on that circuit simultaneously.
As far as cleaning, I clean the doors and the heat shield in the cover as
well as vacuuming out the chaff and "droppings" from the tray and duct. I
figure the reflected heat off the clean heat shield could make a difference
from roast to roast. I don't clean the drum as I figure that is what I want
to absorb the heat. The bean cup and the duct are cleaned in the sink or
dishwasher occasionally. The heat shield is fairly easy to take off, just
two screws, but be careful as the punched slotted holes in the ends are very
sharp (learned the hard way!!!). I have found a significant amount of chaff
behind the shield and blocking the holes at the ends so I suspect it is a
good idea to clean it occasionally.
I would say my experience has also been that the roast "progresses" rapidly:
seconds matter. There is a huge difference in one minute at the end of the
roast. Carefully weigh the green beans so you have repeatability. I keep
notes with the time I roast, how much of what beans, time to first crack, to
second crack and general impression of results. I, contrary to the
instructions, often roast 9 ounces at a time since this gives me about 8
ounces roasted and it slows the roast profile somewhat. I really like the
Alpenrost but there is some "mystery" in learning its use.
I hope this helps..