Zenith 19" Chromacolor II service suggestions

[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.

[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.