Quote:
Originally Posted by old_coot88
Not sure what is meant by spot knocking. But rebuilt CRTs would frequently arc after installation due to less-than-perfect cleanliness by the rebuilder.
The "cattle prod" applied to the pins would cause debri particles inside the tube to incandesce white and fly around, eventually welding themselves in place somewhere, out of harm's way.
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Sometimes particles or burrs on the gun parts in a finished CRT would field emit electrons causing brightly illuminated areas on the screen of the tube, even though the electron gun was turned off. Internal arcing was often observed, as well. The "spot knockers" typically used a HV supply to draw excessive current from these burrs to "burn them out" or dislodge them to a place somewhere out of harms way, as you described, eliminating the field emission "spots". Similar process, for sure.
jr
On Philco turn on, my rounded top 50T-1400 fired up (with a gentle variac ramp-up) after sitting un-used for over 40 years, with sound, video, decent HV and Horizontal but very short vertical. Most parts and tubes are original. Philco must have used pretty good parts in these sets.
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08-15-2014, 10:06 PM
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