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Adjustment Procedures
1780R-Series Service Manual
5–45
d. Set the VECTOR GAIN to VAR.
e. Move the subcarrier vector to the Vectorscope CRT compass rose using
the variable VECTOR GAIN control.
f. Connect the 10X probe from the test oscilloscope to A6TP379 on the
Vectorscope board. Set the test oscilloscope vertical deflection factor to
0.5 V/Div, Input Coupling to DC, and sweep rate to 10 ms/Div. Check
that the generator 180_ Subcarrier is set to On. (For PAL, check that the
U Subcarrier is On.)
g. Adjust Demod Offset (A6R369) for 1 volt of DC at the non-subcarrier
time.
h. Touch the GO TO DIFF GAIN pad on the Vectorscope CRT.
i. Check that SINGLE is selected.
j. If necessary, move the vector to the CRT compass rose using the variable
VECTOR GAIN control.
k. Check that the test oscilloscope 10X probe is connected to A6TP379.
l. Adjust DG Offset (A6R167) for 1 VDC at chroma time.
m. Check that the LEFT DISPLAY-VECT mode light is on. Touch the GO
TO DIFF PHASE pad and check that SINGLE is selected.
n. Remove the 10X probe from the test point.
o. Use the VERT POS control to move the vertical interval line of the
display trace to the graticule baseline (0 IRE for NTSC; 0.3 V for PAL).
p. Rotate the Precision Measurement control until the chroma overlays the
vertical interval line on the waveform display.
q. Press the 1780R-Series REFERENCE SET button.
r. Check that the D PHASE readout on the Waveform CRT is 0.00_.
NOTE. Do not press the REFERENCE SET button during the remaining portion
of this step.
s. Rotate the Precision Measurement control for a PHASE readout of
–5.00_.
t. Adjust Demod Gain (A6R370) for 5 major divisions of deflection
between the chroma and the vertical interval lines.