Well I should not be be surprised this Zenith just came to life with almost no effort, but I still kinda am...
I replaced the bulb with one from my junk box that appears to have closer spaced elements, re-soldered the clipped HO tube screen resistor, jumpered the HV reg socket (more on that below), replaced the focus diode, and cleaned/adjusted controls.
The original HV reg was supposed to be a 6JK6 or 6JH6 but IIRC a 6HZ6 was installed (by previous owners)...The 6Js are designed with pins 7 and 8 BOTH connected to the plate where as the 6HZ only connects one of those pins to plate. The chassis was designed so the damper is effectively disconnected from the fly if the HV reg tube is unplugged...Since the substitute lacked the internal jumper the damper was disabled WITH the reg plugged in...I added a jumper between pins 7 and 8 and the HV came up, and it was easy repair work from there on. That tube sub made it impossible for the set to work as found (possibly why it was found necked in a TV shop basement).
HV is about 22KV max where the schematic calls for 25KV...I'll let that slide for now.
The neons don't light in use so I guess they are an over voltage protection measure. My 20BC50 parts chassis lacked those bulbs so I had to use a randomn one.
It is working pretty darn good now. Once the metal back, a kind member here is sending me, arrives all it will need is an antenna to be complete.
