Elenco Electronics AM-550TK Instruction Manual download pdf (Page 19)

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Figure 13

Generator

.02μF

Amps COM V/Ω

GND

R15

GND

R15

DYNAMIC MEASUREMENTS

Turn the power OFF and connect the VOM and RF

generator as shown in Figure 13.

Set the VOM to

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

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.

DETECTOR AND ACG TEST

If your RF generator does not have amplitude modulation or you do not have an oscilloscope, go to Section 3.

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.

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.

SYSTEM CHECK

Figure 14

.02μF

Oscilloscope

Generator

GND

R15

GND

R15

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. Increase the

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

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.

DETECTOR BANDWIDTH TEST

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Elenco Electronics AM-550TK Instruction Manual Page 19

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