Help with a Admiral Portable TV ,1950's

[Magnavox300]

Hi, I am new member of this excellent forum, and this is my second post.
I just picked this nice Admiral up for $20.00.
Are these any good? I thought it was a great design, and in pretty good shape too. Only missing the antenna. Can't wait to clean it up, and recap it.
Since I am new to this hobby, (started my first TV just a few weeks ago),
I was wondering if there was any thing in particular I should be careful of, or watch out for when removing the chassis.
I just got it home today, and hooked up a RF modulator, there was clear sound, but there was also a constant loud buzz or humming. I couldn't get the picture still, and it seemed like the humming sound was possibly interfering with the picture.
Any help from the pro's would be welcomed!

Magnavox300