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

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! :)

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