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Adjustment Procedures
5–46
1780R-Series Service Manual
NOTE. Repeat parts p. through t. of this step, if necessary, for proper deflection.
u. Touch the GO TO DIFF GAIN pad on the Vectorscope CRT. Check that
SINGLE is selected. Use the variable VECTOR GAIN control to
position the burst vector to the CRT compass rose.
v. Use the Precision Measurement control to move the chroma of the
differential gain display to the graticule baseline.
w. Press the REFERENCE SET button.
x. Rotate the Precision Measurement control for a D GAIN readout of
5.0%.
NOTE. Rotate the control so that the chroma line is moving upward until a D
GAIN readout of 5.0% is obtained.
y. Adjust DAC Gain (A7R322) for 5 major divisions of deflection between
the chroma line and the graticule baseline.
NOTE. Turn the Precision Measurement control back to obtain the 0.0% D GAIN
readout. Reposition the chroma lines to the graticule baseline. Repeat parts x.
and y. of this step to obtain a deflection of 5 divisions when the D Gain readout
is 5.0%. Repeat, if necessary, to check that A7R322 has been properly adjusted.
z. Touch the GO TO DIFF PHASE, DOUBLE and NOISE REDUCTION-
ON pads.
aa. Rotate the Precision Measurement control so the chroma separation is
about 8 divisions.
ab. Adjust DAC Offset (A7R315) for no separation of the vertical interval
lines of the display traces (see Figure 5–17).
ac. Touch NOISE REDUCTION-OFF pad.
ad. Adjust Demod Offset (A7R314) for no separation of the vertical interval
lines of the display traces (see Figure 5–18).
ae. Touch the GO TO DIFF GAIN pad on the Vectorscope CRT. Check that
DOUBLE is selected.
af. Adjust the Precision Measurement control to overlay the chroma lines.
Press the REFERENCE SET button.
ag. Readjust DG Offset (A6R167) to overlay the chroma lines, using the
first packet.