My 2800 arrived today, everything was accounted for and in very good shape. As promised, I checked out the PSU and it was putting out close to 12V AC without a load. However, when I plugged it into the 2800 and measured the voltage input to the 7805, I was getting about 13.5V DC and the heat sink got pretty toasty as a result. Definitely wouldn't recommend using the original Japanese AC adapter unless you need to perform a quick test or something.
Also, I was curious about the RF modulator since it seems to be the only internal difference between the Japanese 2800 and the SVA II. It's part number CA019628 which I found zero information on, so this is definitely a 2800-specific part and not a typical 2600 RF modulator that was simply retuned.