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  TB 11-6625-2488-50/1
(8) Adjust square-wave generator output
frequency to 100 Hz.
(9) Set UUT INPUT SELECTOR switch to 1
CPSX10.
(10) While
observing
both
channels
of
oscilloscope, increase square-wave generator amplitude
until a further increase in input amplitude fails to produce
a corresponding increase in output amplitude (point of
maximum gain). Waveform on channel 2 of oscilloscope
will be a square wave showing no evidence of high
frequency oscillations. If high frequency oscillations are
present, perform b(7) below.
Note. Increasing input amplitude beyond point
of maximum gain may result in ringing and spurious
high frequency oscillations which cannot be
adjusted out and, if left in this condition for any
length of time, may result in a blown fuse.
b. Adjustments.
(1) Adjust R207 (figure 3) until square wave has
a flat top.
(2) Adjust C206 (figure 3) until square wave has
a flat top.
(3) Set UUT INPUT SELECTOR switch to 1
CPSX1.
Figure 3. Fifty watt amplifier, model DCA-50, typical
(4) Adjust C202 (figure 3) until square wave has
bottom interior view.
a flat top.
(5) Set UUT INPUT SELECTOR switch to 1
(10) Replace oscillator with test oscillator (A4,
CPSX10.
(6) Repeat (2) through (5) above until no further
(11) Repeat (1) above.
adjustments are required.
(12) Adjust test oscillator output frequency to 500
(7) Adjust C104 (figure 3) until high frequency
kHz.
oscillations are removed.
(13) Set test oscillator amplitude to maximum.
Measure and record distortion indication.
8. Distortion. a. Performance Check.
(14) Repeat (6) and (7) above. Distortion will be
(1) Connect equipment as shown in connection
less than 5%. If not, perform b(1) through (3) below.
A of figure 4.
b. Adjustments.
(2) Set UUT INPUT SELECTOR switch to
(1) Repeat a(1) above.
DCX10.
(2) Adjust C156 (figure 3) for distortion
(3) Set each decade resistor (A7, table 1) to
indication on distortion analyzer.
400 ohms.
(3) Repeat a(13) and (14) above.
(4) Adjust oscillator (A3, table 1) output
frequency to 5 Hz.
9. Power Output. a. Performance Check.
(5) Adjust oscillator amplitude until distortion
(1) Connect equipment as shown in connection
analyzer (A1, table 1) indicates 100 volts rms. Measure
A of figure 4.
and record distortion indication.
(2) Connect oscilloscope (A5, table 1) to UUT
(6) Connect equipment as shown in connection
DC OUTPUT terminals, using cable (B4, table 2).
B of figure 4. Measure and record distortion indication.
(3) Adjust oscillator output frequency to 5 Hz.
(7) UUT distortion is difference between
(4) Adjust oscillator amplitude until UUT output
distortion measured in (5) and (6) above. Distortion will
waveform displayed on oscilloscope just begins to show
be less than 0.3 percent.
clipping. Distortion analyzer (A1, table 1) will indicate
(8) Repeat (1) and (4) through (7) above at an
100 volts rms or greater.
oscillator frequency of 50 kHz. Distortion will be less
(5) Adjust autotransformer (A9, table 1) to 105
than 0.3 percent.
volts ac.
(9) Repeat (1) and (4) through (7) above at an
(6) Repeat (4) above.
oscillator frequency of 100 kHz. Distortion will be less
(7) Adjust autotransformer to 125 volts ac.
than 0.5 percent.
7
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