Quantum Data 801GC, 801GF, 801GX manual If purity cannot be corrected to acceptable limits

BLU_PIC, GRAY_PIC, GRN_PIC, RED_PIC, WHT_PIC, Flat, Flat Gray, Flat_B, Flat_G, and Flat_R — contd.

Method	The methods used for adjusting purity on a color
	monitor depend on the type of monitor and CRT
	you’re using (for example; Delta, In-Line or Single
	Gun). In most cases, the first step is to degauss
	the CRT.
	Note – For a Delta Gun CRT, turn on only the Red output. A
	solid uniform field of red should be displayed. If the color is
	not uniform, adjust the yoke and the Purity Tabs assembly.
	If purity cannot be corrected to acceptable limits,
	the monitor may not have been properly degaussed
	or there may be a defect in the CRT or purity
	assembly.
Test	Shadow mask warping
Purpose	The purity characteristics of your CRT can change
	over time if you leave it on with a lot of video
	being displayed. This may be due to the CRT’s
	electron beams striking its shadow mask with
	enough energy to cause the mask to heat. This
	internal heating may be enough to cause the
	shadow mask to warp and give bad purity.
Method	Set the purity image to white and allow the monitor
	to run for a few minutes. Any mask warping shows
	up as a change in purity. You can use a color
	meter to measure the change. The BriteBox pattern
	also may be useful for measuring shadow mask
	warping.

4-8 Chapter 4: Built-In Images Model 801GC, 801GF & 801GX¥Rev. X1