Philips 7538, Service Manual

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3.
Adjust R712 to straighten the vertical lines on the left and right sides of the picture.
4.
Adjust R714 to remove any trapezoid distortion (tilt) from the vertical lines on the left and right sides of the
screen.
NOTE : An adjustment of register 80 (Horz Center) in the service test mode may need to done to center the raster
properly on the screen before preforming step number 5.
5.
Adjust R728 to obtain a slight Horizontal overscan on the right and left sides of the screen.
Convergence and Purity Adjustment
NOTE: The Color Purity and Convergence Adjustments described below
should be performed only after installation of a new CRT or Deflection
Yoke Assembly; otherwise, it will not be necessary to remove the rubber
wedges. Minor corrections for purity and convergence can be
accomplished through the use of the Purity and Convergence Assembly
located on the neck on the CRT.
Degaussing the receiver
1
Position the TV receiver so that the screen faces the direction (North, East, South, or West) it will be facing,
while in use.
2
Before the set is turned on, thoroughly Degauss the entire receiver.
a. Move a Degaussing Coil in a circular motion slowly around the sides and the front face plate of the receiver.
b. Withdraw the Degaussing Coil at least six feet before disconnecting it from it's power source.
CONVERGENCE AND PURITY ADJUSTMENT PROCEDURE
Pre-Convergence adjustments (Perform Degauss procedure first)
1 Place the multi-pole Purity and Convergence Assembly with the 2-Y pole Purity Rings directly in the gap
between the G2 and G3 (Focus) Grids. (As shown in Figure 2)
2 Connect a Center Cross pattern or a Crosshatch pattern to the antenna terminals.
3 Set the Green Cutoff control R202 (L-3) to its fully clockwise (CW) position.
4 Set the Green Drive control R205 (L-2) to its fully counterclockwise (CCW) position.
5 Loosen the Yoke Clamp screws, pull the Yoke back and remove the three Yoke wedges.
6 Slide the Yoke all the way forward so that it rests against the bell of the CRT.
7 Tighten the Yoke Clamp screw so that the Yoke does not drop away from the bell of the CRT.
8 Slowly spread and, if necessary, rotate the 2-Y pole purity rings so that the red and blue lines are at least
parallel and preferably coincide at the 6:00 and 12:00 o'clock position. (Refer to figure 3).
Color Purity Adjustment
1 Connect a Solid White Pattern signal to the Antenna terminals.
2 Set the Red Cutoff R201 (L-2) and Blue Cutoff R904 (L-3) controls fully clockwise (CW). Then set the Blue
Drive R907 (L-3) control fully counterclockwise (CCW).
3 Set the Green Cutoff control R202 (L-3) fully counterclockwise (CCW) and the Green Drive control R205 (L-2)
Fully clockwise (CW).