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Performance Verification
1780R-Series Service Manual
4–57
f. Set the test oscilloscope dual trace amplifier controls as follows: Ch 1
Volts/Div to 0.1 V, Input Coupling to DC, Display Mode to Ch 1, and
the Trigger Source to Ch 1. Set the Time Base controls as follows: Mode
to Auto, Coupling to DC, Source to Int, and the Time/ Div to 1 ms.
g. Set the 1780R-Series front-panel controls as follows: Select the
VECTOR GAIN–VAR mode. Press the PHASE SHIFT button to On.
h. Turn the variable VECTOR GAIN control to place the burst vector dot
on the compass rose. (For PAL, use the 135_ burst vector dot as the
reference and the equivalent to the NTSC burst vector dot when
performing parts i. through w.)
i. Use the Precision Measurement control to align the burst vector dot with
the 180_ graticule line.
j. Adjust the generator Variable Burst Amplitude control to display 200
mV burst amplitude on the test oscilloscope (210 mV for PAL).
k. Check that the burst vector dot remains between 178_ and 182_.
l. Set the generator Variable Burst Amplitude control to obtain 404 mV
burst amplitude on the test oscilloscope CRT (424 mV for PAL).
m. Check that the burst vector dot remains between 178_ and 182_.
n. Set the generator Variable Burst Amplitude control to the detent
position. Disconnect the coaxial cable from the test oscilloscope Ch 1
input and 1780R-Series EXT REF connectors. Reconnect a 75 W
end-line termination to the EXT REF connector to terminate the Black
Burst signal.
o. Move the Color Bar signal to the 1780R-Series CH B1 INPUT
connector and terminate into 75 W. Select INPUT–CH B1.
p. Use the Precision Measurement control to align the vector with the 180_
graticule line. Press the REFERENCE SET button so that the PHASE
readout on the Vectorscope CRT is 0.00_.
q. Move the Color Bar signal back to the 1780R-Series CH A INPUT
connector and terminate into 75 W.
r. Select INPUT–CH A. Turn the Precision Measurement control to align
the burst vector dot with the 180_ graticule line.
s. Check that the PHASE readout remains between 358.0_ and 2.00_.
t. Move the Color Bar signal to the CH B2 INPUT connector and
terminate into 75 W. Select INPUT–CH B2.
u. Check Use parts p. through s. as a guide for checking CH B2.