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980 DP 1.4 Video Generator / Analyzer - User Guide
Rev. A1
16.18 BLU_PIC, GRAY_PIC, GRN_PIC, RED_PIC, WHT_PIC
16.18.1Description
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.
16.18.2Test
Purity adjustment.
16.18.3Purpose
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.
Method 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.
16.18.4Test
Shadow mask warping.
16.18.5Purpose
Page 325
June 16, 2017
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