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Originally Posted by Kaye-Halbert TV
Nice clean new-looking seleniums there, and may I add a nice clean chassis overall! Are those seleniums new? I've never had to change any on a CTC-2. On the subject of reproduced CT-100 stuff, has anyone made focus and convergence pots?
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Those selenium diodes are there for looks only; while I have not had a pair fail either, for safety they were replaced electrically with a couple of 1N4005’s.
As you know, the failure of a vertical convergence transformer is particularly insidious because a common failure mode causes a chain reaction that burns out the focus pot. Too much focus current is drawn if the secondary shorts to ground; the 1X2B focus rectifier plate goes cherry, and the pot can literally blister on the outside and melt internally.
While its design voltage rating is unknown to me, the focus pot is the center of a three-element voltage divider with nearly 4 kV at the wiper. While I haven’t had to do it yet, I’ve seen an ordinary linear taper pot successfully substituted for the original one. Personally, if I have to do that someday, I’ll make sure there’s an insulated knob on the shaft before I adjust it.
I had a pleasant surprise when the chassis came out of the cabinet. Notice in the picture the hue control -- the variable cap on the end of the center shaft of the three running back from the front panel. It's in the dead-center position. Exactly where it was after aligning the chrome AFC a year ago.