[drh4683]

20X1C38, 1967. All fixed up and running great now. An original factory wiring error caused the HOT to run way to high. This would explain a new hot installed 4 years after the set was made, yet the rest of the tubes original and good. Even the 6HA5!

After comparison to the schematic, and then the other 20X1C38 sets I had, definitly a wiring error. A 470K resistor was supposed to be wired from 250 B+ to the convergence panel, instead it was hooked to the 200V plate of the horizontal discharge to the convergence panel. Because this resistor was soldered to the plate of the H. discharge, a load was across it lowering the plate to 140 volts. The screen of the 6JS6 is to be running at -60V, but with the lowered plate voltage, the screen voltage went to -45 causing the js6 to run 260-280ma, when its to be running at 220ma!!!
Whats an important note, the 200V plate voltage, and the 250V B+ were next to each other on the Pin boards, so the error was appeared to simply an accident, the resistor was just one pin out of place! I guess thats why RCA ads always bragged about the elimination of "hand wiring errors" in their "new" printed circuit boards! I would have never expected zenith to let this one slip by! 37 years later the problem was solved. Im glad zenith screwed up, it saved this TV because the owners were paranoid to use it!!!!