Reddit reviews PowerBright 100 Watts Japanese Voltage Transformers, Step Up and Down Japan Converter, can be Used in 120 Volt and 100V Countries, Convert from 120V to 100V and 100V to 120V, Universal Outlet Socket
We found 2 Reddit comments about PowerBright 100 Watts Japanese Voltage Transformers, Step Up and Down Japan Converter, can be Used in 120 Volt and 100V Countries, Convert from 120V to 100V and 100V to 120V, Universal Outlet Socket. Here are the top ones, ranked by their Reddit score.
100 WATT STEP UP / DOWN JAPANESE VOLTAGE TRANSFORMER - This step up and step down voltage transformer can be used for small electronic appliances. This is the best step Up/Down Japanese voltage converter on the market.HIGH VOLTAGE TRANSFORMER- This power transformer can be used in 120 Volt countries in North America and Japan is 100 Volts. It will convert from 120 Volt to 100 Volt AND from 100 Volt to 120 VoltCE CERTIFIED VOLTAGE CONVERTER - The CE marking is a certification mark that indicates conformity with health, safety, and environmental protection standards.USE PROTECTED POWER TRANSFORMER - Two outlets on front of the unit, on/off power switch with indicator light. includes free two spare fuses.1 YEAR PARTS & LABOR WARRANTY - Specialized customer service team & technical installation support via email, phone or chat.
https://www.hunker.com/12003435/can-you-use-japanese-appliances-in-the-us
Answer: may be ok, but to be on the safe side you can pick up a step down transformer, less than $20 on amazon.
https://www.amazon.com/PowerBright-VC100J-Transformer-countries-Convert/dp/B00757RYPK/ref=pd_lpo_sbs_60_t_1?_encoding=UTF8&psc=1&refRID=18BMGWNK0W0XJHE3WJ7B
For Japanese consoles in NTSC-U/C regions, you should be fine. They are generally engineered to withstand the higher voltage, however it WILL shorten the overall life of the system due to introducing extra heat in the system (though it probably wont outright kill it, as trying to use NTSC systems in PAL regions would).
If that worries you, there are a few options.
First, you can replace the power supplies. For consoles with external power supplies (like the SNES, Xbox 360, etc.), you can simply buy an equivalent for the US region, and not have to worry about it. For consoles with internal power supplies, you can generally replace the internal power supply with one from your region (as they generally use the same internal voltages), and not have to worry about it either.
Second, use system mods on US consoles. I don't know about 3DO, but there are a few options available for the other two. For Saturn, you can simply buy an NTSC-U/C console, and an Action Replay Pro 4 in 1 cartridge (which you should get anyways for the Saturn), as that will allow you to play most Japanese import games without issues. With the Dreamcast, you could buy the imports, then make CD-R copies of them to play (because the copy protection in the Dreamcast is laughably easy to bypass). You can also install a mod-chip the US Saturn and Dreamcast to play imports as well.
Third, buy a step down converter. I don't know much about them, but something like this would probably be what you're looking for.