Japanese AC power is similar to USA power. However, I believe that Japan uses 50Hz 100V, and the USA uses 60Hz 120V. Europe, on the other hand used higher voltage, typically 200 to 240V, which fries some equipment.

As for your laptop, it should run fine. The important thing is to check your power adaptor. Look underneath it, and you should see something like this:

  INPUT:  50-60Hz 100-240V ~ 1.5A

As long as you've got 50Hz and 100V covered, you're okay!

As for your Mini-Disk, check it too. I don't have a Mini-Disk, so I couldn't check to see a sample range.

I checked my CD player, which said:

   INPUT: AC 120V 60Hz

I'd be worried about using it since it didn't list a range. But since it said:

  OUTPUT: DC 6V 400mA

I should be able to find (or have a Japanese friend find) a suitable replacement power adaptor.

Items such as electric shavers work fine in Japan. They just humm at a different frequency.

As for Hilton turntables, you sometimes need to turn the speed up to 50 or 55 rpms to get it to sound like USA 45 rpms. This may be machine dependent, on whether or not they've been 'converted'.

Japan uses the same electrical plug-types as the USA. Unfortunately, 3-prong (grounded) plugs are less common in Japan, so, if your laptop requires a 3-prong outlet, I suggest you bring along a 3-to-2 prong adaptor.