Zenith 19" Chromacolor II service suggestions

[Kevin Kuehn]

Originally Posted by old_tv_nut

To verify that it's due to focus being sharp (and not a signal problem repairable in the circuitry), try adjusting focus to see if poorer focus reduces it, or try adjusting height or width to see if the moire fringes move.

Focus,brightness(picture control) and contrast(black level) all have influence. About mid brightness is where I tend to like it in low room lighting, however that's were it's at it's worst. What seems to work is brightness slightly past mid and contrast lowered to compensate the harsh whites. All said I'd say the brightness control is more influential than the focus.

[Kevin Kuehn]

Originally Posted by old_tv_nut

To verify that it's due to focus being sharp (and not a signal problem repairable in the circuitry), try adjusting focus to see if poorer focus reduces it, or try adjusting height or width to see if the moire fringes move.

I noticed that turning the color down doesn't change the pattern, it's still there in black and white. If it were a signal problem what circuit module would you suspect? I do have a 27" CCII from Feb 1977 that may have several compatible modules. Luminance for one.

[old_tv_nut]

Originally Posted by Kevin Kuehn

I noticed that turning the color down doesn't change the pattern, it's still there in black and white. If it were a signal problem what circuit module would you suspect? I do have a 27" CCII from Feb 1977 that may have several compatible modules. Luminance for one.

The fact that it's still there in black and white says to me it's not a signal problem. You can verify this by going to black and white and changing the verticsal scan height slightly to see if the moire moves, or possibly by moving the raster slightly up and down by turning the vertical hold control if this set has one.

[Kevin Kuehn]

removed double post.

[Kevin Kuehn]

Yes the vertical hold can be set to roll ever so slow and the moire sure does stay in the same location as the picture rolls by. You only really notice it when there's a large light background such as walls or sky areas. Any detail seems to diminish it. Also it's not distributed evenly across the CRT face, it seems to be predominately in the outside mid to upper left and right fields of the screen. If this was a common thing with these era Zeniths, I wonder if they ever offered service personnel a technical explanation of what physical aspects was causing the effect?

Originally Posted by old_tv_nut

The fact that it's still there in black and white says to me it's not a signal problem. You can verify this by going to black and white and changing the verticsal scan height slightly to see if the moire moves, or possibly by moving the raster slightly up and down by turning the vertical hold control if this set has one.

[old_tv_nut]

So, the moire does not ripple or change polarity at all? Did not expect that.
Edit: or are you saying the ripples change but just stay prominent in the same area? That's what would be expected if it's caused by the interaction of the scan lines and the phosphor pattern. If this is the case, it shows it's not a signal problem because it is modified by the exact position of the scan lines.

[zeno]

1) Your DGS is running normal
2) Moire was explained by Boston service mng. Not in depth. See
internet for that. I learned what I needed.
3) Beware swapping boards. example 9-88 has several flavors, 9-88, 9-88-01,
9-88-02 etc. Not all are subs.

Zeno
LFOD !

[Kevin Kuehn]

I will have to try this again because it's a little difficult to visually process with the picture rolling. My impression was that the moire ripple pattern and location did not change, but as the picture content moves past it becomes more or less predominant. I suppose that effect could also happen because I had the DVD content paused(stationary picture) rather than random content change. Sort of gives the appearance of magnetic interference pattern. I wish I could photograph it better but my camera messes with it and often shows more of a moired rainbow pattern.

same

Originally Posted by old_tv_nut

So, the moire does not ripple or change polarity at all? Did not expect that.
Edit: or are you saying the ripples change but just stay prominent in the same area? That's what would be expected if it's caused by the interaction of the scan lines and the phosphor pattern. If this is the case, it shows it's not a signal problem because it is modified by the exact position of the scan lines.

[Kevin Kuehn]

It would be helpful if you could provide a link, I am not familiar with this Boston service mng. you speak of?

Originally Posted by zeno

2) Moire was explained by Boston service mng. Not in depth. See
internet for that. I learned what I needed.

[Kevin Kuehn]

Here's a picture I just took off my over the air box after pushing the still button. Notice how wave in the blue sky seems the same as the picture below it that I took several days ago. Another frame with the same sky may not show any moire. I really don't understand what triggers it to manifest.

[zeno]

Moire that I have seen is best described as a thumb print.

[old_tv_nut]

Originally Posted by Kevin Kuehn

I will have to try this again because it's a little difficult to visually process with the picture rolling. My impression was that the moire ripple pattern and location did not change, but as the picture content moves past it becomes more or less predominant. I suppose that effect could also happen because I had the DVD content paused(stationary picture) rather than random content change. Sort of gives the appearance of magnetic interference pattern. I wish I could photograph it better but my camera messes with it and often shows more of a moired rainbow pattern.

same

Forget using the vertical hold, and adjust the height very slowly. Moire caused by the CRT should stay in the same area but ripple through.

[Kevin Kuehn]

Originally Posted by old_tv_nut

Forget using the vertical hold, and adjust the height very slowly. Moire caused by the CRT should stay in the same area but ripple through.

I'm not exactly clear on what you mean by ripple through, although I do see the spacing between the shading change, and if I continue changing the height the pattern can even change it's shape. I'm testing with a stationary picture. As Zeno mentions this may not be what most would consider a textbook moire. Sometimes it shows up in smaller area's, but it's more of a rippled shading effect rather than a distinct color changing pattern. If you look at shading at the tops of the two pictures it's almost more a sinusoidal pattern. The finer fingerprint on the right side of the green background is a camera artifact.

[old_tv_nut]

Originally Posted by Kevin Kuehn

I'm not exactly clear on what you mean by ripple through, although I do see the spacing between the shading change, and if I continue changing the height the pattern can even change it's shape. I'm testing with a stationary picture. As Zeno mentions this may not be what most would consider a textbook moire. Sometimes it shows up in smaller area's, but it's more of a rippled shading effect rather than a distinct color changing pattern. If you look at shading at the tops of the two pictures it's almost more a sinusoidal pattern. The finer fingerprint on the right side of the green background is a camera artifact.

You are describing exactly the kind of effects expected due to the CRT and not the signal circuits, so, case closed.