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Performance Verification
WFM 90 and WFM 91 Service Manual
4–11
This procedure verifies the following requirement:
Phase Shift with Subcarrier Frequency Change from F
SC
to F
SC
"50 Hz
(F
SC
"10 Hz PAL): "2°. Phase Shift with Burst Amplitude Change from
Nominal to "6 dB: "2°. Phase Shift with Variable Gain Control Varied from
+3 dB to –6 dB: "1°.
1. Connect a 75% color bar signal to the VIDEO IN connector. Set the input
switch to the 75 W position.
2. Select VECTOR display mode on the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor.
3. Use the Phase controls to position the burst vector on the 180° graticule line.
4. Check that when the television generator subcarrier frequency is changed
"50 Hz ("10 Hz PAL) from nominal, that the display locks, and that the
burst phase has changed "2° or less.
5. Return the subcarrier frequency to nominal on the television signal generator.
6. Replace the color bar signal on the VIDEO IN connector with a black burst
signal.
7. Check that the vector phase changes less than "2° while varying the burst
amplitude from nominal to "6 dB (1/2 to 2X amplitude), using the
television signal generator burst amplitude control.
8. Return the burst amplitude to nominal on the television signal generator.
9. Select VAR GAIN ON from the Configuration menu.
10. Check that the vector phase changes less than "1° while varying the vector
burst amplitude from 1/2 to 1.5 times nominal amplitude using the variable
gain control.
11. Select VAR GAIN OFF from the Configuration menu.
12. Remove the signal input from the VIDEO IN connector.
This procedure verifies the following requirement:
Chrominance Bandwidth: Upper –3 dB Point: F
SC
+ 500 kHz, "100 kHz.
Lower –3 dB Point: F
SC
– 500 kHz, "100 kHz.
1. Connect the precision 50 W cable to the output of the leveled sine wave
generator. Connect the other end of the cable to the 50 W to 75 W minimum-
loss attenuator, and then connect the attenuator to the VIDEO IN connector.
2. Select EXT REF from the Configuration menu.
Vector Phase Stability
Chrominance Bandwidth