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Performance Verification
1780R-Series Service Manual
4–35
25. Check Filter DC Matching
Supplemental: (not listed in Section 2); Matching: Within 10 IRE for NTSC
(70 mV for PAL).
a. Check that a Pulse & Bar signal is applied to the 1780R-Series CH A
INPUT connector.
b. Set the 1780R-Series controls as follows: Select WFM HORIZONTAL–
THREE–LINE. Hold the left FILTER button in until the FLAT, LUM,
and CHROM lights are On. Set the WAVEFORM GAIN to X5. Select
COUPLING–GND on the Configure menu.
c. Check that the three filter lines are within 10 IRE of each other for
NTSC (or within 70 mV of each other for PAL).
d. Select FILTER–FLAT mode, WFM HORIZONTAL–ONE–LINE, and
WAVEFORM GAIN–X5 to Off. Select COUPLING–DC and DC
RESTORER–OFF on the Configure menu.
e. Disconnect the Pulse & Bar signal from the instrument.
26. Check Common Mode Rejection
Requirement: See Table 4–3.
Table 4–3: Common Mode Rejection
Frequency A–B B–B2/B–B3
60 Hz 46 dB 34 dB
15 kHz (Luminance) 46 dB 34 dB
1 MHz 40 dB 34 dB
3.58 or 4.43 MHz (Chroma) 34 d B 34 dB
a. Connect a 60 Hz sine wave signal from a sine wave oscillator to a
dual-input coupler.
b. Connect one side of the dual-input coupler to the 1780R-Series CH A
INPUT connector; connect the other side of the coupler to CH B1
INPUT. Do not terminate.
c. Check that INPUT–CH A and WFM HORIZONTAL–ONE–LINE are
selected.
d. Set the sine wave oscillator output amplitude control so that the display
on the Waveform CRT is 140 IRE for NTSC (1 V for NTSC or PAL).