KV9200 Issues

[vol.2]

First a little background. I got this set in about 1992, and used it sporadically for about 12 years before mothballing it in storage. It worked very well and had a bright tube when I got it, and I didn't put a lot of wear on it myself.

I got it out of storage recently for a project, and it needed to have basically all of the electrolytics replaced. Several of them had corroded away to nothing, and all but a few were way, way out of spec and drying out.

So I finished a full recap, and set it up as per the service manual a

nd the Sams.

It works okay, and is still pretty bright, but it's got a few lingering issues that I'm not sure what to do about.

1) In some material (not all), there is horizontal lines in the colors. This seems to be stronger when I turn down the brightness. So far, it only happens with one of the DVDs I tested. The lines are strongest in the Red, but I have also noticed them in Blue. I don't (or can't) see these lines in other things I have tested in the same DVD player (so far). The DVD that does show these lines seems fine on other TVs.

2) I followed the setup instructions, and it says I should set the BKG dials at halfway, the DRIVE dials at full, and adjust a crosshatch for best grey at the BKG dials. The BLUE crosshatch comes up first, but it's only the vertical lines, not the horizontal lines which take a lot more background to make appear. Red and Green do not appear to have the same issue, and the horizontal lines do appear as bright as the vertical lines. Because of this issue, I was unable to set the white balance this way, and I had to use a black background and just do the whole screen to grey. This eventually worked after a whole lot of back and forth and looking at greyscale images, but I can't help feeling like this issue with the Blue being much stronger vertically is a problem, especially since it doesn't effect the Green or Red.

I was thinking maybe I should try replacing the BKG and DRIVE transistors and see how that goes. I don't know what else I could try. This is the output section of the schematic:





3) The Sam's references a "Beat Pattern," when adjusting the 4mHz trap. It wants me to adjust the fine tuning on strong signal until I get a "beat pattern," and then turn a pot until that goes away. I don't know what a beat pattern is. Any help with that?

4) The Sam's also wants me to use a sweep generator for some of the setup stuff. I don't have one. I have a scope, a signal generator, and a pattern generator. Can I use the function generator in place of a sweep generator in this fashion?



5) The Horizontal Oscillator seems flakey. I followed the instructions, which is to ground the transistor on the Oscillator and adjust the control until the image stops floating, but I couldn't really get it to stop completely. I could get it right to the point when it starts to drift in the other direction, but it floats around enough that it will move back and forth by itself if I leave it alone. I don't know how much of an issue this is, but I thought if it was, I might need to replace a transistor, or maybe a pot with more turns will allow me to get it more accurate?




Thanks