Dynamic Measurements; System Check - Elenco Electronics SUPERHET AM-550TK Assembly And Instruction Manual

DYNAMIC MEASUREMENTS

DETECTOR AND ACG TEST
Turn the power OFF and connect the VOM and RF
generator as shown in Figure 13.
accurately read 2 volts DC and set the output of the RF
generator for 455kHz, no modulaton, and minimum
amplitude. Turn the power ON and slowly increase the
amplitude of the 455kHz signal from the RF generator
Amps COM
GND
Figure 13
R15
If your RF generator does not have amplitude modulation or you do not have an oscilloscope, go to Section 3.

SYSTEM CHECK

Connect equipment as shown in Figure 14.
Set the RF generator at 455kHz, 1kHz at 80%
modulation and minimum output. Turn the power ON
and put the volume control at full clockwise position.
Figure 14
DETECTOR BANDWIDTH TEST
Connect equipment as shown in Figure 14. Set the RF
generator at 455kHz with 80% modulation at a
modulation frequency of 1kHz. Set the oscilloscope to
read .1 volts per division. Turn the power ON and put
the volume control at minimum.
amplitude of the RF generator until the signal on the
oscilloscope is 4 divisions peak to peak. Check the
signal to make sure it is free of all distortion. Leave the
Set the VOM to
V
V/W
Oscilloscope
GND
R15
Increase the
until the voltage at TP3 just starts to drop. This point is
called the AGC threshold with no IF gain. Make a note
of the amplitude setting on the RF generator here:
Turn the power OFF.
Slowly adjust the amplitude of the RF generator output
until you hear the 1kHz on the speaker. If this test fails,
turn the power OFF and check C11, R12, volume
control, D1 and TP3.
.02mF
frequency of the RF output at 455kHz, but increase the
modulation frequency until the output drops to 0.28
Vpp. Record the modulation frequency on the RF
generator here:
This frequency should be greater than 5kHz. Turn the
power OFF.
-18-
____________.
Generator
.02mF
GND
R15
Generator
GND
R15
_________.