Tektronix 422, Instruction Manual

Page: 119 / 213

Performance Check/Calibration—Type 422 AC-DC
32. Check Channel Isolation Ratio
a. Change the fo llo w in g c o n tro l se tting s:
CH 1 VO LTS/DIV
.01
CH 2 VO LTS/DIV 2
CH 1 Input Coupling GND
CH 2 Input Coupling DC
X10 GAIN AC Pushed in
T IM E /D IV .5 ms
b. Connect the low-frequency sine-wave generator to
the INPUT 2 connector w ith the BNC to dual binding post
adapter and the 42-inch BNC cable.
c. Set the low-frequency generator fo r a five-division
display at one megahertz.
d. Set the vertical Mode switch to CH 1.
e. CHECK—CRT display 0.1 division or less in ampli­
tude (channel isolation 10,000:1 or greater).
f. Change the following control settings:
CH 1 VO LTS/DIV
2
CH 2 VO LTS/DIV .01
CH 1 Input Coupling DC
CH 2 Input Coupling GND
g. Connect the low-frequency sine-wave generator to the
INPUT 1 connector with the BNC to dual binding post
adapter and the 42-inch BNC cable.
h. Set the low-frequency generator fo r a five-division
display at one megahertz.
i. , Set the vertical Mode switch to CH 2.
j. CHECK—CRT display 0.1 division or less in amplitude
(channel isolation 10,000:1 or greater).
k. Disconnect all test equipment.
Control Setup
When performing a complete procedure, change the
follow ing control settings and proceed w ith step 33.
CH 1 and CH 2 VO LTS/DIV .05
Vertical Mode CH 1
Partial Procedure
If beginning a partial procedure w ith this step, set the
controls as given under Preliminary Control Settings.
33. Adjust Channel 1 Only Triggering DC Level
PERFORMANCE CHECK ONLY
Steps 33 through 35 are not applicable to a perfor­
mance check. Change the CH 1 Input Coupling
Switch to DC and proceed w ith step 35.
a. Test equipment required fo r steps 33 through 53 is
shown in Fig. 5-19.
b. Change the following control settings:
CH 1 Input Coupling GND
TRIGGERING Coupling DC
c. Connect the 10X probe to the vertical input con­
nector of the test oscilloscope.
d. Set the test oscilloscope fo r a vertical deflection fac­
to r of 0.01 volt/division (0.1 volts/division at 10X probe
tip) at a sweep rate o f 20 microseconds/division w ith the
input coupling switch set to the ground position.
e. Position the test oscilloscope trace to the center hori­
zontal line o f the graticule to establish a zero reference
level. Then set the test oscilloscope input coupling switch
to DC.
f. Connect the 10X probe tip to TP364 (trigger compen­
sation test point, see Fig. 5-21A). Connect the probe
ground strap to chassis ground. Be sure the probe is com­
pensated.
g. Set the LEVEL control to return the test oscilloscope
trace to the center horizontal line (zero reference level).
h. Set the TRIGGERING Source switch to CH 1.
i. CHECK—Test oscilloscope trace w ithin 0.5 division of
the center horizontal line (zero reference level).
NOTE
This tolerance is provided as a guide to correct instru­
ment operation and is not an instrument specifica­
tion.
j. ADJUST—CH 1 DC Level adjustment R57 (see Fig.
5-20) to position the test oscilloscope trace to the center
horizontal line.
34. Adjust Internal Trigger Compensation
a. Set the Channel 1 Input Coupling switch to DC.
b. Remove transistor Q364 (see Fig. 5-21 A) from its
socket.
c. Connect the square-wave generator high-amplitude
output connector to the INPUT 1 connector through the
GR to BNC adapter, 18-inch 50-ohm BNC cable, tw o 10X
BNC attenuators and the 50-ohm BNC termination, in given
order.
d. Set the square-wave generator fo r a one-division dis­
play on the test oscilloscope at a frequency o f 10 kilohertz
in the high-amplitude mode.
e. CHECK—Test oscilloscope display for optimum
square-wave response similar to Fig. 5-21B (this waveform
5-25