Sansui AC with 100 volt ... Plug into 120 volt outlet ?

No, and you need a step down transformer.  I mean it might work for a while and then burn out. 

https://www.hunker.com/12003435/can-you-use-japanese-appliances-in-the-us

erik_squires

No, and you need a step down transformer.

Agreed, absolutely. Note to OP: You'll notice the plug on your Sansui is different from the type of plug used for AC in the US. There's a reason for that.

A simple convertor, 120v down to 100v, decent quality, nothing big or special.

Locate it so you can remember it is there so you don't forget in the future, but like any transformer, a spot with no hum.

It is a simple converter, but you want to make sure the wattage is correct. I believe I read the Sansui consumes 250W so this 500W transformer will work for you with plenty of a safety margin:

https://amzn.to/3smFDiI

Sadly the next size down is too small.

Of course, don’t plug anything into the convenience outlets on the back! :)

rocky1313

Sansui AC with 100 volt ... Plug into 120 volt outlet ?

Both 60hz countries so the transformer should be fine, we have 220v to 250v in some areas and no problems.
The preamp section will be fine, as it’s power supply is no doubt regulated.
But the power amp section will get higher rail voltage, instead of being a 65w x 65w amp, it will become 85w x 85w, circuit should take it. The only thing with a big ? just hope the big power supply caps are over rated to take the higher rail voltage. (circled in red) https://ibb.co/kDkGmqP
Easy to check with a dc volt meter, and their max voltage is on the side of them.
And not a bad idea to check the DC offset. As it will run hotter with more Class-A, so the bias should also be checked..

Cheers George