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Performance Verification
4–38
1780R-Series Service Manual
a. Check that a 5-Step, 40 IRE Modulated Staircase signal is applied to the
1780R-Series CH A INPUT connector. For PAL, use a 280 mV
Modulated Linearity signal.
b. Connect a coaxial cable from the AUX OUT connector of the 1780R-Se-
ries instrument under test to the Ch A Input of a test vectorscope.
Connect an end-line termination to the Ch A Input loop-through
connector on the test vectorscope. (The test vectorscope is another
vectorscope used to check the 1780R-Series instrument being checked.
See the Recommended Equipment List.)
c. Set the controls of the test vectorscope to measure differential phase in
the double-trace mode. Null the first step and record the dial reading.
Null the last step and record the dial reading. Subtract the smaller
reading from the larger reading to obtain the measurement.
d. Check that differential phase is ≤0.25_.
e. Set the controls of the test vectorscope to measure differential gain
between the first and last steps of the staircase.
f. Check that differential gain is ≤0.25%.
g. Move the coaxial cable from the AUX OUT connector to the PIX MON
OUT connector on the 1780R-Series being checked.
h. Check Repeat parts c. through f.
i. Disconnect the test vectorscope from the PIX MON OUT connector of
the 1780R-Series instrument being checked. Disconnect the 5-Step
Staircase signal from the CH A INPUT connector of the instrument
being checked.
29. Check Linear Waveform Distortion
Requirement: Pulse Overshoot & Ringing: ≤1% of applied pulse amplitude.
Pulse & Bar: ≤1% of applied pulse amplitude. 25 ms Bar Tilt: ≤1% of
applied bar amplitude. Field Square Wave Tilt: ≤1% of applied square wave
amplitude. 2T Sin
2
Pulse-to-Bar Ratio: 1:1 ±1%.
a. Apply a modulated 2T Pulse & Bar signal, through a 75 W feed-through
terminator, to the 1780R-Series CH A INPUT. Do not go through the
Switcher module.
b. Check that the 1780R-Series controls are set as follows: INPUT–CH A,
REF–EXT, and WFM HORIZONTAL–ONE–LINE.
c. Check that there is 1 IRE or less for NTSC (7 mV for PAL) of overshoot
and ringing on the 2T bar.