CT-100 color sync issue?

[Phil Nelson]

I should clean house more often. I was rummaging through junk boxes and found these:



The cases are identical to the original, although the legs are a little thinner and closer together. The original has the codes 1107330 -1 4-54. These are stamped ED and have codes 1107863 -3 3-66 and 1107863 -1 4-77. If the last three digits are date codes, then maybe I have one from each decade.

I'll bend/thicken the legs on one of them and try it out.

I'm going to build the video preamp described in the 1956 RCA Broadcast News article so that I can bypass the front end. If the problem disappears, that tells us it was located upstream, I guess.

I also ordered some 100% DeOxit and leetle brushes to see whether cleaning the front-end sockets helps.

Phil Nelson

[Phil Nelson]

I got a new NTE358 crystal and cleaned all sockets the Pete way. Cleaned the tuner, too, while I was at it.

The original crystal was certainly off frequency, judging by what happens when you swap crystals without changing anything else. Assuming the new one is correct, the other old crystals that I found are also off by varying extents.

I redid the color AFC alignment with new crystal in place. The picture is strong and noticeably more stable than before. I think the cleaning was well worth the effort. We still have evil color bands, though.



I turned contrast & brightness way down on this one to show how stable and well defined the color bands are.



Maybe I'm messing up somewhere in the color AFC procedure. The darned thing feels like it's so close to locking . . . .

Phil Nelson

[old_tv_nut]

Originally Posted by Phil Nelson

I turned contrast & brightness way down on this one to show how stable and well defined the color bands are.



Maybe I'm messing up somewhere in the color AFC procedure. The darned thing feels like it's so close to locking . . . .

Phil Nelson

There are 10 (maybe 12 with vertical retrace) color bands, meaning the oscillator frequency is off by 600 -720 Hz. So either the oscillator frequency is tuned this far off and the AFC can't pull it in, or there is something wrong with the phase detector [edit - or the reactance tube circuit] that is forcing it off to one side.