This is the same picture but with more brightness and contrast (to see the uneven roasting)

All your pictures look like beans that have somehow not encountered the heat that they should have. The first picture could lead one to believe that you just got unlucky with some of the beans being immature, but that would be odd for a grade 1 Ethiopian.

Do you get the same, normal agitation sounds during the roast? Anything sound off/different? Have you tried the same approach with a lower charge weight?

Hi Tom,

the Gene roaster is brand new, the temperatures seems to be OK, sounds are normal, sometimes is hard to distinguish the crack, but I believe that this is normal. The same situation happens when roasting 200 or 250g.

As I said, the visibility of uneven roasting is less visible when coffee is cracking with high temperature (240 C) but I think that these light spots shouldnt happen even on lower temperatuers...

But I have noticed during roasting, that these "light spots" are visible from time when coffee is getting cinnamon color or light brown color, so very soon, not only at the end...

What's your yellowing time, first crack time and full roast time with the pre-heating?

Did you measure the voltage? Worthwhile to check if your roasts are going too slow. Mine tended to vary depending on time of day, but were always a bit on the high side, so not an issue. Voltages were lowest during what I would think of as the highest demand times. 120-125 Volts here with a 2 V drop when heater cycles on.

How's the coffee taste?

The temp reading on the Gene isn't much of an indicator since it's not reading bean temp. I found on my Gene that the beans didn't always look super evenly roasted, but tasted great. Yours may look more uneven that mine typically were though. Some beans varied more than others. Never had any issues with bean scorching, but maybe different at 240V?

I believe you have a voltage issue. You have set the machine correctly for roasting the amount of beans.

Though I have 120V here, when I lived in our former home, I was receiving 114V and could not roast effectlvely. It took a Variac to resolve it for me on 120V. I found that the machines performs best for me with 119.7V under load.

I have never used a Gene, but I do use a DIY roaster that can get uneven results. Some of your beans look as if they were between first/second crack. Do you see a correlation between the size of the bean and the color, if your Ethiopian has various bean sizes, then the larger beans will not roast as fast as the smaller. Just a thought.

Your Gene really behaves different then mine. The temperature profile of a Gene will vary a lot with little fluctuations in voltage. The voltage in my house is pretty constant and high. Also different heating elements behave differently. With my old heating element the Gene roasted much faster then with my new heating element. Every Gene is different and that makes it very hard to share profiles.