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#1
03-14-2010, 04:13 PM
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Adjusting the vertical size and linearity on RCA TV's
Is it me, or are these RCA's the biggest PITA to adjust the vertical height and linearity on? You can spend the longest time trying to get it right, then you get to the point on the control where you start to lose the vertical hold, so you have to mess with that too. You get it just about right, then realize that one of the controls is all the way on one end, so you adjust it again, finding that you can get the picture to look decent but if you turn the linearity or height just a touch too far, then the picture height flips over and gets screwed up and you have to "reset" the controls and start over.
I think just about every single RCA I've ever worked on is annoying like this, even the ctc-40 solid state sets. I've tested capacitors, resistors, and the tubes of course. There just doesn't seem to be a "cure" for this other than trying to redesign the circuit. Am I missing something here? I just don't like RCA's vertical circuit at all. Throw in the vertical centering control if its a roundie and you have a never ending dynamics to mess with. I can set up a Zenith including convergence from scratch in less time than it takes to get good linearity on an RCA. Were these RCA's this touchy and annoying to adjust when new? On a Zenith, you can pinpoint perfect height/linearity in about 20 seconds and the controls don't have an impact the other one like on RCA's.
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#2
03-14-2010, 04:26 PM
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It's not you. I've had the same problem with every RCA tube set that I've worked on over the past 20 years.
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#3
03-16-2010, 02:37 AM
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I believe RCA used open-loop linearity correction, which is always ready to drift. My CTC-5 drifts in height, linearity and frequency (because they all interact, if any one of them drifts the other two do also). Zenith developed a current-feedback circuit at some point in their design history that eliminated the linearity drift.
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Linear Mode
