KCS109C Chassis Horizontal Issue (maybe!)

[Chris K]

Hi all. I purchased 2 cosmetically beautiful RCA 17 inch 17D8185 televisions last week. Both have strong 17CDP4 CRTs with excellent cutoff. The tubes run at a high 8.3 volt filament voltages.

The first one I have worked on has been completely recapped, controls cleaned and all tubes tested and working. They are all original tubes. I have a complete NOS tube complement on order and I'll replace all of them when they come. The picture is fantastic with deep blacks and wonderful grey tones. There is, of course, an issue.

I tried photographing this but I couldn't capture it. In my generator's crosshatch pattern, the horizontal lines are perfect...crisp and bright. The vertical lines from the top to the bottom of the screen have a funky anomaly. They look like they are made up of a very fine zig-zag pattern about 1/4" wide with maybe 10 zig-zags per vertical line inch. It seems to be a horizontal issue but I can't seem to adjust it in and there is only the horizontal hold pot to make horizontal changes. Does anyone have an idea as to what this may be and what I might do to fix it?

Thanks all!!

Chris

[zeno]

Tough one. If you either adjust the width or centering ( to see edge of scan) is
the raster itself distorted ?
I would something besides a generator also.
Maybe try the AGC also.

73 Zeno
LFOD !

[Chris K]

Could the 1N60 diode in the video detector cause something like this? I have good germanium 1N34A replacements if I need to replace it.

[old_tv_nut]

What kind of crosshatch generator do you have?
Does adjusting the fine tuning help?
Typical serviceman's crosshatch generators with non-standard sync waveforms can cause trouble depending on the set design. If the problem does not appear with a good source like a DVD player, don't worry about it.

[Chris K]

Sencore VG62. I’ll try my modulated computer hookup tonight

[Chris K]

The picture is over bright and the fuzziness around the text and numbers are artifacts from the camera. Picture is crisp and bright. Lateral waviness is still there but not as noticeable.

Should I replace the detector diode? Would it make any difference with regard to this horizontal issue? Should I just wait for all of the NOS tubes to come and start troubleshooting then when the tubes are off the table as an issue?

Weird Question...the centering tabs on the rear of the yoke...there are 2 of them on this model and they might have gotten moved in the disassembly/reassembly. The image is centered in the screen. Can they have an effect on this? The doughnut shaped plastic back cover of the yoke that has the centering tabs on it is a bit warped and it came off the yoke when I pulled the chassis out. It clips on the yoke with tabs and the tabs are not keyed so it is possible to reassemble the yoke and back cover/centering tabs 60, 120 or 180 degrees out of phase when I put it back on. Still, the picture is centered. Just asking so I'm not missing anything obvious.

Thanks
Chris

[old_tv_nut]

The detector diode is not the problem here. It either works or doesn't. Since you have a picture, it's working. If the problem exists with a good video feed, then you need to look at AGC and sync separation.

1) Did you try the fine tuning? Tuning too high in frequency can make video detail overemphasized and affect sync. Also make sure it's not so far off towards lower frequency that you could be receiving the lower sideband of your modulator by mistake.

2) Try adjusting the AGC down and up from present setting to reduce/increase the signal level/contrast. If the detector output is too large or too small it could cause sync problems.
3) If the AGC adjustment doesn't improve things, wait until you know you have good tubes and then proceed with trouble shooting.

[Chris K]

I solved the earlier horizontal issue by replacing some very hard to get to caps in the horizontal section. The circuit board on this set has a large shield on the bottom that severely limits access. Anyway, got it done and the horizontal is fine.

The upper 25% of the picture is stretched vertically though. When a video puts someone's head in that area, they look like The Coneheads.

Could this be a magnet problem on the CRT? New vertical tubes. The vertical linerarity and vertical height do have some effect if I squash the picture down a bit but even doing that, there are still wide trace lines in the top part of the image area. Any suggestions as to what I should start looking at?

Thanks all.

Chris

[Electronic M]

Vertical stretch at the top can be caused by bad caps, tube(s), bad resistors, and or inductors.

Check voltages on the vertical tube(s) and waveforms if you can. Sometimes if all is right you need to play with centering along with the height and lin to get vertical right.