Is it a 19" CRT - 19AP4 ?
Here is the Zenith Service Manual - scroll to the bottom:
http://www.earlytelevision.org/tv_sc..._diagrams.html
I have the "Bryon" 24H21 Chassis porthole TV - no doors but the bezel looks exactly like yours.
Looks like your Power Supply is not in the proper position.
They are indeed very collectible and nice TVs.
Carl