To fix horizontal red, green and blue lines creeping into the top of the
> NTSC monitors:
>
> 1. Press the 'Menu' button
>
> 2. After the menu appears, press 'Enter' and 'Degauss' at the same time. If
> the screen is then degaussed, that means that you didn't hit them at the
> same time so try again.
>
> A. Hopefully you just entered 'Service mode'. You should see a display
> resembling this:
>
> OTHER >163 91
> V. BLANKING <60>
>
> B. The number 91 is the feature we are adjusting (in this case, vertical
> blanking).
>
> C. The number 163 is the value that vertical blanking is currently set to.
>
> 3. Use the 'Menu' and 'Enter' buttons to scroll to #91 if you're not already
> there.
>
> 4. Use the + and - buttons to adjust the vertical blanking. As you move up
> or down, you should
> notice the problematic lines going away.
>
> 5. When you find the right setting, press 'Degauss' and the word 'Write'
> will appear on the screen.
>
> 6. Immediately press 'Degauss' again to save.
>
> 7. Turn the monitor off and then on again and you're ready to roll.
http://archives.bengrosser.com/avid/2003-01/msg02329.htm