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As for that glowing spot in the center of the CRT screen after power down, some sets had a circuit that had a cap connected from the brightness circuit (feeding the grid 1 of the CRT) to B+. Idea is that when the set is turned off, the B+ will collapse quickly, and the cap will take longer to discharge. This will force the CRT tube into cutoff thus blocking the electrons that would produce the spot. Once this cap is discharged, the cathode will be cold.
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