Tektronix Option 10 Service Manual page 90

HDTV
Option-Performance Check and Adjustment Procedures
24X5B12467B Options
Service
3. Check TV (Back-Porch) Clamp (CH 2 only)
a. Set:
50 MHz BW LIMIT On
CH 1 VOLTSIDIV 500 mV
CH
2
VOLTSIDIV 50 mV
A SECIDIV 2 PS
SLOPE
-
(minus)
TRIGGER MODE AUTO LVL
TRIGGER SOURCE
LINE
b. Connect the sinewave oscillator output via a 75-a cable
to the CH 2 input connector.
4.
Check Back-Porch Reference
a. Set:
CH 2 Input Coupling GND
A SECIDIV 1 PS
TRIGGER SOURCE VERT
b. Set the trace to the center horizontal graticule line using
the CH 2 POSITION control.
c. Connect a 100%-modulated composite video signal
from the TV mainframe linearity generator via a 7542 cable and a
75-a termination to the CH 2 input connector.
c. Connect the composite sync output from the TV
d. Set the CH 2 Input Coupling to TV CLAMP.
mainframe linearity generator via a 7 5 4 cable and a 75-S2
termination to the CH 1 input connector.
e. CHECK-That the back-porch level is within 1 division
of the center horizontal graticule line.
d. Set the oscillator to produce a 60-Hz, 6-division display.
Adjust the oscillator frequency control to produce as stable a
display as possible.
f.
Connect a white flat field HDTV video signal via a 75-a
cable and a 75-a terminator to the CH2 input connector.
e. Set:
CH 2 Input Coupling
TV CLAMP
A SECIDIV 20 p s
TRIGGER SOURCE CH 1
TRIGGER COUPLING Ll N ES
g. Repeat part e.
h. Disconnect the test equipment from the instrument.
5. Check Triggering
f. CHECK- Display amplitude is 0.75 division or less.
a. Set:
g. Set:
CH 2 VOLTSIDIV 100 mV
CH
2
Input Coupling 1 M a DC
h. Set the oscillator to produce a 6-division display.
i. Set the CH 2 lnput Coupling to N CLAMP.
CH 2 VOLTSIDIV 10 mV
CH 2 Input Coupling 1 M a DC
A SECIDIV 2 PS
At
On
TRACKING On
TRIGGER MODE AUTO LVL
TRIGGER COUPLING DC
b. Use the A REF OR DLY POS control to align its cursor
with the second vertical graticule line.
j.
CHECK- Display amplitude is 0.75 division or less.
c. Use the A control to produce a A t reading of 1 ps.
k. Set:
CH 2 VOLTSIDIV 200 mV
CH 2 Input Coupling 1 M a DC
I. Repeat parts h through j.
d. Connect the pulse generator output via a 50-ln cable, a
50-Kt 10X attenuator, and a 50-a termination to the CH 2
input connector.
e. Set the generator to produce a signal that has a negative
pulse 3 divisions in amplitude, 1 p s wide, and a period of
approximately 15 ps. Use the A control to produce a At reading
m. Disconnect the test equipment from the instrument.
of 15 ps.