On the RCA, there is no ion trap that I can see... only a deflection yoke as the focus is non-adjustable electrostatic. The "arcing" or more like a continuous tiny "fizzling" in the neck of the CRT seems to be around some tiny metal plates within some internal glass rods, not the beam electrodes themselves.

The Admiral is a wood cabinet model with a wooden X over grill cloth. Chassis is 30B16S and CRT is 10BP4 as you surmized. I purchased from the original owner... set sat in a basement since the late 50s unused. It worked when they put it away, but didn't when they checked again before selling it. Hope no serious damage was done in repowering. Looks like a fusable resistor is gone, perhaps that protected things. Appears to be completely unmolested, but I have a thick layer of dirt to remove. I love the dual chassis setup and it looks like it will be far easier to work on than the RCA... which forces you to become a contortionist with the soldering iron and solder.