The ThinkVision C220p Diamondtron tubes are sensitive to altitude, ambient temperature, and magnetic field, as this may cause color degradation at the corners of the screen.

ThinkVision C220p (6735) CRT monitor.

Perform the following steps to correct the color degradation using on screen display Purity control:

1. Set the monitor resolution to 1600 x 1200 @ 85 Hz
2. Run a program on your computer that displays a completely red background. ensure no area of the operating system's desktop is visible.
   
3. Press the Menu button on the monitor to activate the on screen display menu
4. Reset the ThinkVision C220p to the factory defaults settings by using the Options / Factory Default entry
   

   

5. If necessary adjust the size of the image to extend to the top and bottom of the screen using the on screen displays Image Position/Size menu items
6. Adjust the geometry of the image using the on screen displays Image Shape menu items
7. Using the Color menu item select a preset color temperature of the display of 9300K
   

   

8. From the Image Quality sub-menu select the Purity setting from the on screen display
   

   

9. Adjust any corner that exhibits color degradation using the on screen display controls until the color is corrected.
   

   

10. After ensuring all 4 corners are correct, save the settings and exit the on screen display menu.

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