Tektronix 1740A Series, User Manual

Page: 133 / 368

Performance Verification
4–30
1740A/1750A/1760 – Series Service Manual
25. Burst Phase with Burst Amplitude Change
Requirement – Phase Shift with Burst Amplitude Change of 6 dB: 2
°
.
a. Remove the color bar signal from the CH-A INPUT. Move the black
burst signal from the EXT REF INPUT and connect it to the CH-A
INPUT. Leave the CH-A INPUT terminated.
b. Select MULTIPLE DISPLAY. Vector and waveform displays selected.
c. Check – that while varying the sync generator Variable Burst amplitude
control from 20 to 57 IRE (145 to 400 mV PAL) on the waveform
display, that the burst vector changes
2
°
on the vector display.
26. Vector Phase Shift with Variable Gain Change
Requirement – Phase Shift with Variable Gain C3 to –6 dB:
0.5
°
.
a. Select VECTOR DISPLAY.
b. Remove the terminator from the CH-A INPUT.
c. Position the center dot on the Vector Cross Hairs. Position the burst
vector to 0
°
.
d. Enter the GAIN menu and select VARIABLE ON.
e. Check – that the burst vector changes 0.5
°
while varying the
VARIABLE GAIN control (bezel knob) from minimum gain to setting
the burst on the compass rose.
27. Channel Phase Match
Requirement – Phase Shift with Video Input Channel Change: 1
°
.
a. Move the black burst signal from the CH-A INPUT to the EXT REF
INPUT. Leave the EXT REF INPUT terminated in 75
b. Connect the color bar signal via a 75 termination to the dual-input
coupler. Connect the dual-input coupler to the CH-A and CH-B
INPUTs.
c. Select EXT REF. Enter the GAIN menu.
d. Set the RED vector to the 0
°
graticule on the compass rose using
VECTOR PHASE and VARIABLE GAIN controls (bezel knobs). If
desired, press the CLEAR MENU button to remove the readout.
e. Check – while changing between the CH-A and CH-B INPUTs, that the
phase change is
1
°
.
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