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Performance Verification
1780R-Series Service Manual
4–47
c. Check and/or set the 1780R-Series controls as follows: LEFT DIS-
PLAY–VECT, RIGHT DISPLAY–WFM, REF–EXT, and WFM
HORIZONTAL ONE–LINE.
d. Press the MEASURE button to On. Select DIFF GAIN, SINGLE, and
NOISE REDUCTION–OFF on the Vectorscope CRT menu.
e. Check that the VECTOR GAIN–VAR is On. Turn the variable VECTOR
GAIN control so that the modulation vector dot is located on the
compass rose as displayed on the Vectorscope CRT.
f. Use the VERT POS control to position the Waveform CRT trace to the
50 IRE graticule line for NTSC (0.8 graticule line for PAL).
g. Insert the 5% Signal Attenuator between the coaxial cable and the CH A
INPUT connector.
h. Check that the trace on the Waveform CRT moved downward 50 IRE to
the 0 IRE graticule line within a tolerance of ±2.5 IRE for NTSC. (For
PAL, the trace should move downward 50 mV from the 0.8 graticule line
to the 0.3 graticule line within a tolerance of ±2.5 mV.)
i. Remove the 5% Signal Attenuator. Leave the Staircase signal applied to
the CH A INPUT connector.
j. Press the REFERENCE SET button so that the D GAIN readout is 0.0%
on the Waveform CRT.
k. Turn the Precision Measurement control in a direction that moves the
trace downward five divisions to the 0 IRE graticule line for NTSC (0.3
line for PAL).
l. Check that the D GAIN readout on the Vectorscope CRT is between
4.8% and 5.2%.
m. Turn the Precision Measurement control so that the D GAIN readout is
0.0%.
n. Set the generator 5-Steps button to On.
o. Select DOUBLE and, if desired, NOISE REDUCTION–ON.
p. Turn the Precision Measurement control so that the first step location for
the traces are overlayed.
q. Press the REFERENCE SET button.
r. Turn the Precision Measurement control so that the fifth step location on
the trace overlays.
s. Check that the D GAIN readout on the Vectorscope CRT is equal to or
less than 0.2%.