I Have a beautiful RCA 19" remote controlled portable black and white tv with the KCS 149AA chassis. It has a like new crt. It has one problem I can't locate. The background has has dark vertical striping (Please see the attached photo). At first I thought it was yoke ringing. I substituted the yoke with no new results.
I replaced the Horizontal output, damper and video out recapped the electrolytics and film capacitors. That took care of other minor issues. It originally had very bad horizontal linearity. The middle was squished and the left was 150% of the right side and the linearity coil did nothing. A bad cap in that circuit took care of that problem. The cage around the flyback is all there. I was thinking there was radiation into the video section. Could the flyback be of fault?
It runs cool and current draw is normal. It's a very uneven pattern. The ringing of yokes is even usually on the left only with notable jagged scan lines. Has anyone run into this before? I have earlier set with the KCS 143 chassis which is basically the same but is series strung. It doe not have this issue.The set produces a great picture otherwise. Any help would be greatly appreciated. Thanks...Jeff

205085

Barkhausen oscillation?

Check the lead positioning of the CRT socket and yoke plug wires. Try moving them with an insulated tool and see if the bars move. I remember an RCA factory tip about a similar issue with some of their sets.

When I was switching out H outputs I notice after the set ran for a couple of minutes I would see a tearing of 2 lines on the right side when tuning on the lower UHF channels only. That was with a 6JB6A. I put the regular 6JB6 back in and the barkhausen was gone. Is the "A" version a stronger tube? Do you think what I have is another form of barkhausen getting into the IF or video circuits? How would you correct this? Thank...Jeff

If you have an oscilloscope you can check the H output grid directly, and the yoke by capacitance coupling (wrap a new lead a couple turns around a yoke wire), the B+ and the video. Checking the video tells you if it could be getting in the antenna, checking the B+ tells you if it's conducting through the B+. Also beware poor grounds on circuit boards if this set uses them...Poor grounding can cause all kinds of nonsense.

I've done some checking by pulling tubes and watching the screen. All the way to video out the lines are there and don't shift when rocking the horiz hold. When the video out is pulled the lines are still there but will shift with the horiz hold. What does this suggest?....Jeff

Does this appear only with weak signal or no signal, or also with strong signal? That would help diagnose RF or video.
I don't think A vs. Non-A tubes makes a reliable difference, it's just any particular tube may cause a problem.
Agree with checking lead dress and grounds.

No signal as I stated shows up without the video output tube installed. The A vs non A thing was a barkhausen issue the showed up on lower UHF channels. I just went back to the non"A" didn't display the issue. This was a totally different issue which was resolved. The issue now is the dark vertical bars in the background

Barkhausen oscillation?That doesn't resemble Barkhausen interference that I've seen. My Hallicrafters T-67 showed a classic case of Barkhausen, a single squiggly vertical line running from top to bottom of the screen (right through the news lady's face, in this pic):

https://antiqueradio.org/art/hallit-6708.jpg

You can read more about Barkhausen in my T-67 restoration article:

https://antiqueradio.org/hallit-67.htm

Regards,

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html

I was referring to another problem I encountered while switching horizontal output tubes which is barkhausen and it looks exactly as you have pictured except mine was on the right side...Jeff

No signal as I stated shows up without the video output tube installed. The A vs non A thing was a barkhausen issue the showed up on lower UHF channels. I just went back to the non"A" didn't display the issue. This was a totally different issue which was resolved. The issue now is the dark vertical bars in the background

I wouldn't waste time trouble shooting with video output tube removed, as the set will never be operated that way.

I was reading about this I think in an issue of the PF reporter that this was caused by a resistor that has gone up in value. It was quite a while ago so I dont recall where though. My 17" Crosley has this but not as heavy though.

Seems like it was in the video or horizontal oscillator circuit. Have you checked the carbon resistors? You might have one that drifted, especially the high value stuff 470K and up.

Take a look at the below link for RCA Application Note AN-151. Good info to help determine if it's video or horizontal scan related. There's a real wealth of info in the Archives at the One Electron website.

https://www.one-electron.com/Archives/RCA/RCA-AppNotes/RCA%201952%20AN-151%20Minimizing%20Ripple%20and%20Interference%20i n%20Horizontal-Deflection%20Circuits.pdf

https://drive.google.com/file/d/1fj0lOlm9DNBZynJJOiiIime2qXqFLENU/view?usp=share_link PHOTOFACT LINK