Quantum Data 881 User Manual page 999

BLU_PIC, GRAY_PIC, GRN_PIC, RED_PIC, WHT_PIC
Description
Test
Purpose
Method
Test
882 Video Test Instrument User Guide (Rev A.35)
A solid blue (BLU), gray, green (GRN), red, or white (WHT) box fills the active video area.
Only the white fill has a secondary version. It can be changed to a black fill by pressing the
Step key. The BLU_PIC image is shown below.
Purity adjustment
To produce correct colors in a displayed image, the electron beams from each of the three
(3) guns in the CRT should strike only their matching phosphors. A white image shows
patches of various colors on a monitor with bad purity. The purity adjustment(s) should be
performed before doing any brightness or color tests. In some cases, purity adjustments
involve loosening and repositioning the yoke, in which case purity should be adjusted prior
to doing any geometry tests.
The methods used for adjusting purity on a color monitor depend on the type of monitor
and CRT (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
appear. 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.
Shadow mask warping
561