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Performance Verification
1780R-Series Service Manual
4–21
r. Move the VAC output signal from the CH B3 INPUT to the CH A
INPUT. Connect a coaxial cable from the CH A INPUT loop-through
connector to the +Input of the test oscilloscope Differential Comparator.
s. Connect another coaxial cable from the PIX MON OUT connector,
through a precision (0.2%) 75 W terminator, to the Differential Compara-
tor –Input.
NOTE. The precision terminator is listed under Auxiliary Equipment. It is also
supplied with the Return Loss Bridge.
t. Set the 1780R-Series RIGHT DISPLAY to WFM, INPUT button to
select CH A, and WAVEFORM GAIN–X5 to Off.
u. Set the test oscilloscope Differential Comparator controls as follows:
Volts/Div to 10 mV, Input Coupling (both) to DC, and BW to 5 MHz.
Set the Time Base Time/Div to 1 ms.
v. Check that the signals displayed on the test oscilloscope are nulled
within ±20 mV.
w. Move the coaxial cable from the PIX MON OUT connector to the AUX
OUT connector. (Check that the AUX OUT signal is applied through the
precision terminator to the test oscilloscope.)
x. Set the test oscilloscope Volts/Div to 2 mV.
y. Check that the signals, displayed on the test oscilloscope, are nulled
within ±5 mV.
z. Disconnect the VAC signal from the CH A INPUT connector. Discon-
nect the coaxial cable from the other CH A INPUT connector and the
test oscilloscope.
aa. Disconnect the coaxial cable and precision terminator from the AUX
OUT connector and the test oscilloscope.
ab. Apply a 50-kHz signal from the leveled sine wave generator, through a
50-to-75 W minimum loss attenuator, to the CH A INPUT connector.
Connect a 75 W terminator to the remaining CH A INPUT loop-through
connector.
ac. Check that RIGHT DISPLAY–WFM, INPUT–CH A, REF–EXT, and
WFM HORIZONTAL–TWO–LINE are selected.
ad. Set the generator output amplitude to display a 700 mV peak-to-peak
display on the Waveform CRT. Use the VOLTAGE CURSORS,
ABSOLUTE, SEPARATE, CURSORS 1, and CURSORS 2 measure-
ment mode to be sure that the amplitude is 700 mV.