Quote:
Originally Posted by Electronic M
The 10" and 12" glass CRTs didn't need the doorknob, but many chassis of the day were designed to drive both of those and a 16" metal cone CRT....it was less of a production hasto to make a chassis that drove some glass and some metal CRTs have the cap in the HV cage regardless of the CRT type than pick and choose a flavors of basically identical chassis off the line.
Doorknobs continued in color TVs (which had metal cones later) until around 1956...the RCA TM-21 broadcast monitor had one and was built into the 60s.
Doorknobs are still made today for X-ray machines (based on the datasheets) and we're stocked by mouser and digikey when I last need to order one a year ago....they are very expensive. Also there's really only 2 choices in physical mounting: ASE or metric thread on the bolt holes in the terminals...If you need a terminal to be a stem or something special you have to machine something that will do the job and thread into the cap you get....I had to do a good bit of clever fabrication to fit the 3 replacement doorknobs I installed in my RCA 21CT55...
If your CRT has outer dag and a ground spring making good contact between it and chassis you could probably get away with just flat out removing the doorknob and not replacing it...
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My picture tube I believe does have an outer dag coating and some ground springs, so maybe I can just remove the doorknob capacitor in my tv altogether and just wire the new 1 Megaohm 1 Watt resistor from the 1B3 socket straight to the high voltage anode via a terminal strip bolted to the old doorknob capacitor hardware.
Because I looked at the price of a 500pF 15kV doorknob capacitor and they're over $100 a pop!
