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Adjustment Procedures
1780R-Series Service Manual
5–37
p. Check that FILTER-CHROM and ONE-LINE are still selected.
q. Set the television test signal generator for Horizontal Unlock.
r. Use the 1780R VERT POS and HORIZ POS to center the green-magenta
transition on the Waveform CRT.
s. Set the WFM HORIZONTAL MAGNIFIER to 0.25 ms/DIV.
t. Check for minimum green-magenta transition amplitude on the
Waveform CRT display. Typical amplitude is between one and two trace
widths.
u. Set the television test signal generator for Horizontal Lock. Disconnect
the Color Bar signal from the 1780R instrument.
v. Set the 1780R MAGNIFIER to OFF.
w. Disconnect the Color Bar signal from the instrument.
31. Adjust Chroma Filter Position and Gain
a. Connect the output of the leveled sine wave generator, through a
50 W-to-75 W minimum loss attenuator, to the 1780R-Series CH A
INPUT. Check that the remaining side of the loop-through input is
terminated into 75 W. Check that a Black Burst signal is applied to EXT
REF.
b. Set the leveled sine wave generator output frequency to 3.58 MHz
(4.43 MHz for PAL).
c. Check and/or select INPUT-CH A, REF-EXT, WFM HORIZONTAL-
ONE-LINE, and FILTER-FLAT on the 1780R-Series instrument. Check
that COUPLING-DC is selected on the Configure menu.
d. Adjust the leveled sine wave generator Amplitude Multiplier and Output
Amplitude control for a display of 100 IRE (700 mV for PAL).
e. Select the 1780R-Series FILTER-CHROM mode.
f. Readjust Chroma Gain (A2R828) to obtain the same signal amplitude
for both the CHROM and FLAT positions of the FILTER. Switch several
times to check for optimum adjustment setting.
g. Disconnect the sine wave signal from the 1780R-Series CH A INPUT
but leave the terminator connected to this input.
h. Select COUPLING-GND on the Configure menu.
i. Adjust Chroma Offset (A2R732) to obtain the same DC level when
switching the FILTER between FLAT and CHROM. Switch several
times to check for optimum adjustment setting.