I know this thread is a couple of years old, but I’m about to purchase one of these and found it helpful in my research, so I figured this would be the best place to add any additional pertinent info.
I found this eBay feedback left in the past month that gives some more detail (and pics!) on the different versions—particularly the U.S. vs. Japanese domestic version.
Sadly, no 230v gutshot for comparison, but I’m guessing that the 220-240v models differ from each other in the same way as below; and, as was touched on earlier in this thread, but I don’t think said explicitly: the 100-130v models all use the same element and temp sensor, and the 220-240v models use a second set.
Thanks to anonymized eBay user “r***g” for the following:
“Really happy i have the USA 120v version and the JDM 100v version. looked inside both of them & they are 100% identical down to every tiny smd part other than 2 resistors to regulate the motor speed on the circuit board. The US has 2 300ohm [1watt]* resistors JDM model has a single 10ohm [1watt]* resistor. you can remove the 10ohm and put in two 300ohm. if you don't the pump just runs a bit faster, resistance and inductance of the heater is the same/very close, motor is identical HTH others”
* “r***g” originally had these as three watt, but added the following note to their review:
“small follow up, the resistors are 1watt not 3watt. 3watt will be too large to physically fit.”