I would like to hear from anyone who is running a FreshRoast SR 500, 540 or 800 on 230-volt mains by converting to 120-volt 50-herts. As a retired EE, I know all about the theory, and I'm aware of the poor state of many Chinese-made converters. I'm seeking actual experience. Thanks!

Before getting a converter, you might check the possibility that the FreshRoasts are built for both voltages with series/parallel heaters and dual tap fan motors. In that case, shifting a few wires will do the trick.

I reached out to the manufacturer of the FreshRoast roasters. Here's what they said:

I usually do not recommend using a converter, many have done this and have been successful. But, as soon as the converter or the power supply spikes, the machine is done and will not work. There is a protection circuit on the control board that will blow, and the machine will be useless. The power supply is 1650 watts, 60hz, (50hz will only mess with the fan motor over time), 120V (Not 110V, it will not get hot enough on 110V).

Why not simply get a large transformer with slow start since the frequency apparently only affects the fan motor? Probably as expensive as a decent convertor at that power rating.

Can you elaborate a bit on a transformer vs converter? I'm now in India and there is a complete dearth of roasters available here. I have both an SR800 and SR500 in Nicaragua and would love to bring one of them here. I now use a Hive but having to roast that way every three days is a chore for this old man.

The vast bulk of "converters" are transformers. When referring to a "transformer", most folks think of a two (or more) coil device that transforms the voltage and isolates from ground. So-called "converters" are simply autotransformers, being a single coil device with (usually) multiple taps. These do not isolate from ground. There are other, lab-quality, converters that transform, isolate or not, change the frequency, voltage regulate and so on. These are expensive devices that one would likely not use at home. Another class of converter is commonly called a Variac (which is actually a brand name). It's the same as an autotransformer, but has variable instead of tapped outputs.

I;d check with the manufacturer if they'd recommend using a transformer and if so if an autotransformer is fine (should be). Autotransformers are almost half as expensive...

I heard back from Sam Skaling of Fresh Roast. A 3000w transformer would be the way to go but would only work 220v to 110v. Then a Variac to bring it to 120v. Too much stuff for my new style of living a month here, a month there and keeping it as simple as possible. I suppose it will be coffee sent from the few roasters here. I will really miss this part of the hobby.