Voltage Modification on Japanese units

Go ahead with older equipment made more than 10 years ago.

Back then, maybe where prices were similar between units worldwide, it has always been easier for manufacturers of some higher priced equipment to use transformers with a primary 115-0-115v and depending on connections of this tap, can easily work with voltages of 115v or 230v.

If we are talking about Japan then this statement is false!
Japanese gear runs on 100Volts. The US runs 120Volts. Often the Japanese gear can be rewired or a switch set for 120 volts if you are importing something from Japan but you do have to be careful as not all domestic Japanese gear will run on anything but 100Volts. An example of the latter is the Technics SP-10 made for the Japanese market.

However there are a couple of solutions if you run into this. The obvious one is you can get an isolation transformer that goes from 120 Volts to 100 Volts. If you do this the transformer should be rated at double whatever the maximum draw of the equipment is so as to prevent the transformer from distorting the 60Hz sine wave.

The other thing that can be done is you can have a technician wire a much smaller transformer (and thus less expensive) to 'buck' the line voltage down from 120 Volts to the 100 volts that the product needs. This is a lot less expensive because the transformer only needs to make about 15-20 volts at the current needed by the product. This is especially helpful with smaller devices as often the bucking transformer can be installed internally.

Depends on the kit.

With a lot of kit, the same transformer could be used for 100 V and 220 V depending on the wiring. This was a money/time saving thing for the manufacturer. Better to order 1 transformer that could do both than 2 different models.

Each configuration requires a different fuse however. Make sure you adjust accordingly.

Not all gear was made this way.

Best,
E

Go ahead with older equipment made more than 10 years ago.

Back then, maybe where prices were similar between units worldwide, it has always been easier for manufacturers of some higher priced equipment to use transformers with a primary 115-0-115v and depending on connections of this tap, can easily work with voltages of 115v or 230v.

This has changed somewhat quite a number of years ago, so to protect the revenues of your dealers. Equipment shipped as 0-230v or 0-115v transformer cannot be rewired.

Changing or customising a similar transformer can be done with a change in the sonics for the better or worst.