Performance Check/Calibration—Type 422 AC-DC
h. Return the Channel 1 VARIABLE VOLTS/DIV
control to CAL.
i. Repeat steps b through h for minimum trace shift for
check c and f.
14. Check/Adjust Channel 2 Step Attenuator and
Variable Balance
a. Set the vertical MODE switch to CH 2.
b. Position the trace to the center horizontal line with
the Channel 2 POSITION control.
c. CHECK—Change the Channel 2 VOLTS/DIV switch
from .05 to .01. Trace should not move more than 0.1
division vertically.
PERFORMANCE CHECK ONLY
Front-panel adjustment; can be adjusted as part of
performance check.
d. ADJUST—Channel 2 STEP ATT BAL adjustment
R121 (see Fig. 5-12A) for minimum trace shift as the
Channel 2 VOLTS/DIV switch is changed from .05 to .01.
e. Set the Channel 2 VOLTS/DIV switch to .05.
f. CHECK-Rotate the Channel 2 VARIABLE
VOLTS/DIV control throughout its range. Trace should not
move more than 0.2 division vertically.
NOTE
This tolerance is provided as a guide to correct
instrument operation and is not an instrument
specification.
g. ADJUST—Channel 2 Var Bal adjustment R135 (see
Fig. 5-12B) for minimum trace shift as the Channel 2
VARIABLE VOLTS/DIV control is rotated throughout its
range.
h. Return the Channel 2 VARIABLE VOLTS/DIV
control to CAL.
i. Repeat steps b through h for minimum trace shift for
check c and f.
15. Adjust Common-Mode Current
PERFORMANCE CHECK ONLY
This step is not applicable to a performance check.
Change the following control settings and proceed
with step 1f>: CH 1 and 2 VOLTS/DIV, .05; CH 1
Input Coupling, DC; vertical Mode, CH 1; TIME/DIV,
.5 ms.
a. Change the following control settings:
CH 1 and 2 VOLTS/DIV .05
Vertical Mode ALT
TIME/DIV ,5 ms
b. Position both traces to the center horizontal line with
the Channel 1 and 2 POSITION controls.
c. Connect the 10X probe to the test oscilloscope input
connector.
d. Set the test oscilloscope for a vertical deflection of
0.02 volt/division (0.2 volt/division at 10X probe tip), DC
coupled, at a sweep rate of five milliseconds/division.
e. Ground the input of the test oscilloscope and posi
tion the test-oscilloscope trace to the center horizontal line.
f. Connect the 10X probe tip to the common-mode
current test point (common emitters of Q224 and Q234;
see Fig. 5-13A). Connect the probe ground lead to chassis
ground..
g. CHECK—Test oscilloscope display for three divisions
or less offset from the center horizontal line (see Fig.
5-13B).
NOTE
This tolerance is provided as a guide to correct instru
ment operation and is not an instrument specifica
tion.
h. ADJUST—Common-Mode Current adjustment R215
(see Fig. 5-13A) for optimum balance of common-mode
current in each channel as shown by equal spacing from the
center horizontal line. Balance must occur within three divi
sions of the centerline.
i. Disconnect all test equipment.
j. INTERACTION— Check steps 16 - 18.
Control Setup
When performing a complete procedure, change the fol
lowing control settings and proceed with step 16.
C H I Input Coupling DC
Vertical Mode CH 1
5-17
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