just bought a 16" 1951 zenith porthole

[Dangler]

It sounds like it wasn't "fully restored". At the very least it's going to need the power supply recapped from your description of the hum. I wouldn't run it any more until you get at least that much done.
You should get a service manual, either downloaded from a lot of sites or someone here who has one.
You should post the model number and/or the chassis number.
There are lots of friendly people here who will help all they can.