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Originally Posted by Electronic M
is it a good idea to keep using the field neutralizing magnets on the front of the CRT with a 21FJP?
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I tried to use them with a glass tube, but they are too weak to fix impurities in the center of the screen. I also gave you that plastic ring with the hairpin magnets on it right? CTC-9 chassis use the same thing, I'd strap that to the back of the tube and see if you can get good purity between that and the edge purity magnets from the CTC-4. The hairpins come in pairs and I think one is missing. You'll want to remove that one...
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Second those knurled metal things on the outside ends of the convergence yoke that point towards the back of the set, are they the static convergence adjusters?
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More like beam positioning, but call it what you will. Basically you center all the dynamic convergence controls, then use the knurled knobs on the conv yoke to set up a roughly converged center cross pattern. From there, you follow the Sams dynamic proceedure RELIGIOUSLY till it starts to look better. Then you do it 5 more times till it looks right.
Oh, don't forget to do red purity before any of that other stuff. Purity first, then convergence. ETF has the CTC-4 Sams posted if you don't already have one.
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This set is nearly a decade older than any color set that I've worked on before so it is a real learning experience of how they designed them in the early days, and a good chance to sharpen my trouble shooting skills and put those skills to the test.
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Actually, the 4 was one of the easier sets I've worked on. Most things remained about the same after the CTC-4 and 5, which were each special in their own ways. The 4 detected color on different axes than any other set before or after: R-Y and G-Y vice the typical R-Y and B-Y that came later, or I/Q that came before, along with having high level demod. The 5 had a funky demodulator circuit using 12AT7's. The CTC-7 and everything thereafter looks the same on paper, subtle changes only. Most of it is different tube types, but later ones also shed an IF stage or 2 due to getting tubes with higher gain.