Calibration— Type 544/RM544
SWEEP
LENGTH
C557K
Corner Rail Removed
C290C
GEOMETRY
HIGH VOLTAGE
X10 CAL
XI CAL
■ R861
R840
S R544
1 g566 .
C290B
C290A
C502C
CS03C
REGIS
R569
X I00 CAL
RS6S
EXT
GAIN
R S I 3
R325
R 5 1 9
(.S i/O
C557F
C557H
( A1
-150
VOLTS
R6t 6
AMPl
R943
Fig. 5-2. Calibration odjuitmont location* (right »id* view).
NOTE
NOTE
Don't adjust the — 150 VOLTS control unless one or
more of the supplies is actually out of tolerance.
Remember that the calibration of the entire instru
ment is affected by changes in the power supply
voltages. All the positive voltage power supplies de
pend upon the — 150-volt supply measurement ac
curacy.
2. Check Regulation and Output Ripple— Power
Supply
NOTE
* When checking for proper regulation of the power
supplies at the lower line voltage limit, the ac line
voltage should contain no more than 3% sine-wave
distortion.
a. Monitor the regulated output of the—150-volt supply
with the VOM. The test point location is shown in
Fig. 5-1.
b. Connect a IX probe from a lest oscilloscope (item 1)
to the —150-volt test point and check the output
ripple amplitude. The maximum ripple voltage is
given in Table 5-3.
Ground loops con cause an erroneous ripple meas
urement. (Ripple due to ground loops is the same
frequency as the line; low-voltage power supply
ripple is twice the line rate.) One way to avoid rip
ple due to ground loops is to temporarily disconnect
the chassis ground wire in the power cord by using
an ungrounded 3-to-2 wire line-plug adapter. Then
use a ground lead from the signal probe to make a
ground connection to tho oscilloscope chassis at the
location shown in Fig. 5-1. The probe will then pro
vide the only ground connection between the two
instruments. The "test oscilloscope" is item 1 while
the term "oscilloscope" or "instrument" refers to
the oscilloscope being calibrated.
c. Slowly increase the output of the variable autotrans
former to 126.5 vac lor 10% above the design-center
line voltage for which the instrument is wired). The
dc output voltage should remain essentially constant;
typically within 2% of that obtained with design-cen
ter line voltage. The ripple voltage should not ex
ceed the maximum peak-to-pcak amplitude given in
Table 5-3.
d. Repeat steps 2a through 2c for each supply.
«
5-3
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