I now have the set off the top of it's stack and am trouble shooting it so I decided to revive my thread.
The old girl is doing some funny things. First off the screen is intermitantly going dark for VERY brief intervals (blink of an eye brief). HV is steady at about 24.4-25KV.
The CRT socket it ticking!
I can't see any arcing in the vicinity of the focus lead in the socket, but that sound is a dead give away. Is it possible/reasonable for a socket on a 1971 Zenith to arc? What voltage from the focus lead is the socket meant to with stand? It currently has a solid 7KV or more on it when it should have only 4.1KV according to the schematic. When I first powered up the set the focus was at arround 1KV but now tends to stay up at 7KV....I find this wierd because previous issues were all stuff dragging down the voltage, and were eventually compensated for by modifying the set to increase the focus voltage to return it to speck. I wonder if whatever was causing the voltage to be low has cleared up, and if removing my mods will fix it.
There is also very loud intermitant corona at a solder terminal that the focus lead goes to in the HV cage.
I'm going to try some things.
Anyone have any potentially helpful ideas or oppinions on this that they would like to share?