Filter
Top Products
Performance Verification
1780R-Series Service Manual
4–37
button to CH B1 when setting the display reference amplitude and then
select INPUT B1B3 to check common mode rejection).
u. Disconnect the dual-input coupler and the sine wave signal from the
instrument.
27. Check Differentiated Steps
Requirement: Step Attenuation: ≥40 dB, 3.58 MHz, or 4.43 MHz. Step
Amplitude: Within 2% of flat display.
a. Connect a 5-Step, 40 IRE Modulated Staircase signal from the television
test signal generator, through a 75 feed-through terminator, to the
1780R-Series CH A INPUT connector. For PAL, use 280 mV modula-
tion.
b. Set the 1780R-Series controls as follows: Select INPUT–CH A and
FILTER–DIFF mode. Press the WAVEFORM GAIN button to select the
VAR mode.
c. Adjust the variable WAVEFORM GAIN control so that the differentiated
steps are 100 IRE or 714 mV in amplitude for NTSC (set to 1 V for
PAL).
d. Use the VERT POS control to position the tips of the differentiated steps
to the graticule centerline on the Waveform CRT.
e. Check that the differentiated steps are within 2% or 14.3 mV (for NTSC)
of each other when comparing the lowest amplitude step with the highest
amplitude step. For PAL, 2% is equal to 20 mV.
f. Use the VERT POS control to position the waveform blanking level to
the graticule baseline (0 IRE for NTSC; 0.3 V for PAL).
g. Press the WAVEFORM GAIN button to select X5 (not VAR–X5).
h. Check that the subcarrier attenuation is 40 dB or 2 IRE for NTSC
(≥20 mV for PAL).
i. Set the FILTER selection to FLAT and the WAVEFORM GAIN–X5 to
Off.
j. Leave the Modulated Staircase signal connected to CH A INPUT.
28. Check Non-Linear Waveform Distortion
Requirement: Differential Gain at Aux Video Output and Pix Mon Output:
≤0.25%, 10% to 90% APL. Differential Phase at Aux Video Output and Pix
Mon Output: ≤0.25_, 10% to 90% APL.