Quantum Data 980 DP User Manual page 208

980 DP Video Generator - User Guide Rev. A4
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 may also be useful
for measuring shadow mask warping.
Page 208 July 14, 2014