Greetings, and welcome to VK from northeastern Ohio (Fairport Harbor, 35 miles east of downtown Cleveland near Lake Erie, as my mini-profile shows).
Zenith was a very good brand of TV, radio and audio,
until Goldstar got its hooks into the company in the '80s and ruined its reputation for good.
The older Zeniths, radios as well as TVs and stereos, were excellent performers in their day and can be again, given the right kind of TLC and restoration. I have had several Zenith TVs and liked them all (my favorite being my first Zenith TV, a 1963 VHF-only 23" console model K2739), and am currently collecting vintage/antique Zenith radios from the '50s and '60s; the one that started my radio collection is a Zenith H511Y table model from 1951, which I still have -- and it still works fairly well, even with the original capacitors (including the 3-section filter in the power supply).
You will find a grand bunch of people here at VK, ready to help you with any issue or problem you may have with your new (to you) Zenith porthole TV -- or for that matter any kind of vintage electronics. I've been a member here since 2003 and have gotten much help and good advice regarding troubleshooting of the radios in my collection.
One thing everyone in this forum will tell you regarding restoration of old radios/TVs is to recap the set before even thinking about plugging it into the AC line. "Recap" in this context means to replace all wax paper capacitors and the filter capacitor(s), although if you are in a hurry to check out your new acquisition, replacement of the filters should be enough, with replacement of the other capacitors to follow as soon as possible. It is important to replace the filters in very old radios and TVs because old caps can short and burn out the power transformer (in sets so equipped), as well as causing other problems such as hum, instability of the sync signals in TVs, and can even reduce the sensitivity of old radios.
Good luck finding your porthole Zenith. Once you get your set working at peak efficiency, you will not be disappointed. Zenith of Chicago did not cut corners with their radios or televisions; until the '80s, anything bearing the Zenith name and their trademark "lightning bolt" logo was very high-quality home entertainment gear. "The quality goes in before the name goes on" was Zenith's slogan for decades, until Gold Star of Korea took over the company in the late 1980s and moved it overseas. Liking Zenith stuff as much as I do, I was very disappointed when the announcement was made that the company was leaving Chicago, but unfortunately, the die was cast and the Zenith Radio Corporation, as we once knew it, is no more. That's why I think it is so important for all us VK members to keep our Zenith equipment running at peak efficiency
, as we will never see this kind of fine workmanship and sound/video quality, as went into the old Zenith TVs and radios until GS took over, ever again.