CTC-16 - good retrace blanking? - Videokarma.org TV - Video

frenchy · #1 05-01-2005, 02:50 AM

My CTC-16 is now recapped and working great except I do notice retrace lines show up if I turn up the brightness past a certain point. And no this is not those occasional digitized 'data' lines that show up, I have those also on some channels and I know those are normal. These are the standard retrace lines that show up on all channels in the same place and only on high brightness setting.
Just wondering what the state of retrace line blanking was at this stage of the tv manufacturing game (1966) and I'm not knowlegeable enough to look at the schematics and say, oh yeah, there's the blanking circuitry right there. This set has a super original picture tube, it's set on the lowest bias setting and with the screen pots near the top end (set up using service switch) I get more than enough brightness. I have an old tv repair book from '65 that talks about retrace blanking circuitry as sort of a new thing in color TVs, which is why I was wondering if this set should have it or not, or how good. Would love to be able to crank the brightness up to what it is capable of without the lines.
Thanks...Frenchy

jstout66 · #2 05-01-2005, 10:44 AM

Well..... I get a bright picture on my CTC-16 but get a few retrace lines if I really crank it up, and I have a Grade AA RCA black Matrix tube from 1977 in mine. I had another CTC16 that had none. In my set I have now I changed the 12BY7 and they about went away. I suspect it's something in the video circuit, or it could be your picture tube. The tube could show a good picture, but still be a tad weak, especially being 40 years old. I'd try a new 12BY7 and see if you get improvement. I saw the screen shots on your set and you have pretty good color on it. Those old 21FJ's were pretty durable.

oldtvman · #3 05-01-2005, 03:29 PM

put a scope on the b+ line and see if you have any ripple going to the vert osc. most problems like that can be caused from power supply problems

frenchy · #4 05-01-2005, 08:11 PM

Quote:

Originally Posted by oldtvman

put a scope on the b+ line and see if you have any ripple going to the vert osc. most problems like that can be caused from power supply problems

I don't own a scope but... I have totally recapped the electrolytics so hard to fathom how I would still have any ripple in there because of them. What could cause ripple besides bad electrolytics? I do have some hum in the sound when I turn the tone control to anything below 100% treble now which I didn't really notice before. I'm sort of sorry I recapped all these electrolytics as some recommended now, it was working better than this before I did it, including the retrace lines...Frenchy

frenchy · #5 05-01-2005, 09:48 PM

Hmmm I think maybe I THOUGHT the retrace was worse after the recap but now I think it was perhaps due to three overvalued resistors I had replaced, after I did that (after the recap), the picture was quite a bit brighter than before on the same bias and screen settings. I decided to screw the 'single line setting' because that's giving me too much retrace. 1. I set the brightness on high; 2. set contrast about midway; 2. tweaked the screen pots till I had a white picture AND retrace went away. Then tweaked the drives to brighten up more. I'm happy again, much better now. Also - all this and tweaking the AGC and it has vastly improved the blooming on highlights, now I can turn the contrast almost full on which also helps the on the retrace....Frenchy

frenchy · #6 05-06-2005, 02:09 AM

hee hee somebody gave me some surplus tubes and one of them must have fixed the sound hum cuz it's gone now. Yeah!...Frenchy