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Section IV
Paragraphs 4-35 to 4-44
4-35. A ten to fifteen minute warmup at normal line
voltage ( nominally 115 or 230 volts) and power supply
output voltage measurements are always recommended
before making any other tests or adjustments.
Refer
to paragraph 4-36 before making any power supply
adjustments.
4-36. POWER SUPPLIES. .
4-37. The power supplies in this instrument are ex-
tremely stable and will require infrequent adjustment.
The output voltages may be measured at regular inter-
vals or as a first troubleshooting step but unnecessary
adjustment should be avoided.
A defective tube or
component may overload the power supply and lead
you to believe that the power supply is not functioning
properly.
4-38. As long as the power supply regulator is func-
tioning properly, you need not know the absolute values
of the power supply output voltages. However, when
power supply adjustment is necessary, you should use
a voltmeter
with
a known
calibration
accuracy.
4-39. Regulation of the power supply can be checked
by varying the power line voltage between 103 and
127 volts.
The output voltage will vary only slightly,
if at all, from the value measured with a 115 volt line.
Loss of power supply regulation is most easily de-
tected, as a sudden large increase in power supply
ripple as the line voltage is raised and lowered ± 10%
from 115 volts.
4-40. When
the power supply output voltages are
within limits with the line voltage at 115 volts, ad-
justment is
not necessary.
Do NOT adjust in at-
tempt to refine the existing control settings.
4-41. To test the power supplies proceed as follows:
a. Measure power supply outputs. They should be
within the limits shown in table 4-5.
b. If the voltage is outside the limits in the table
•
(- 200 volt set) for - 200 volts. This con-
trol
is
in the center of the power supply deck with
access
only
from
the front side of the chassis.
c. You may wish to check the regulation of each
power supply as the line voltage is varied between
Table 4-5.
Regulated Power Supply Tolerances
Nominal
Voltage
Nominal Ripple
at 115/230 vrms
Input
Output
Voltage
Range
-200
(violet wire)
+300
(red wire)
+27
(brown- orange wire)
10 mv
10 mv
---
200
±8 volts
300
±12 volts
unregulated
Model 606A
103 apd 127 volts.
All regulated voltages should
re-
main within ± 1% over this
range of line voltage.
d. Measure the ripple voltage on the various sup-
plies.
They should approximate the values indicated
in table 4-5 with the power line voltage set at 115 or
230 volts.
4-42. AUDIO OSCILLATOR.
a. Set RANGE
540 KC-1800KC
MODULATION SELECTOR
b. Turn POWER switch to ON.
INT 400
c. Connect an $: e Model 400D AC VTVM to output
tap on audio transformer ( yellow lead on signal tie
point behind rf output meter).
Connect ground lead
of voltmeter to ground.
d. Set
ttl
ie
n
4
m
) s4e
!
(l
t
44, potentiometer for 3.2
volts.
This
middle one in the row of
five potentiometers on top of the modulation deck.
4-43. CRYSTAL CALIBRATOR.
a. Set CRYSTAL CALIBRATOR to 100 KC.
b. Connect an electronic counter to pin 2 of the
crystal oscillator tube ( V10).
c. Acliusi tlmmyr (r..4..1) for exactly 100.000 KC.
This trimmer is the ceramic capacitor on the right
side ( as viewed from the front) of the instrument
under the modulation deck.
d. Set CRYSTAL CALIBRATOR to 1 MC and read
counter.
Reading should be between 999.900 and
1000.100 KC.
e. Set CRYSTAL CALIBRATOR to 100 KC and read
counter.
Reading
should be
between 99.990 and
100.010 KC.
f. Set trimmer C41 to best compromise between
the above limits.
g. Turn CRYSTAL CALIBRATOR to OFF.
4-44. TUNE OSCILLATOR AND AMPLIFIER.
Note
This procedure should be performed only if
there is a definite indication that the oscil-
lator is off frequency.
It should NOT be
done on a routine basis.
a. Set
CALIBRATE
cursor to align with
FRE-
QUENCY centerline
ATTENUATOR
. 3 VOLT
MODULATION SELECTOR
CW
FREQUENCY dial
low end of one
of the bands ( except highest frequency)
b. Connect
RF
OUT
terminal
to an electronic
counter, such as the
Model 524B/C/D with a Model
525A Converter.
4-10
00170-2
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Troubleshooting
