Elenco AM Radio Kit - Manual (Page 13)

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Adjust your VOM to read 9 volts and connect it to test point 7
(TP7) as shown in Figure 8.
Make sure that the battery, or a 9 volt power supply (if available),
is properly connected and turn the power ON. The voltage at
TP7 should be between 4 to 6 volts. If you get this reading, go
on to the next test. If your circuit fails this test, turn the power
OFF and check that the integrated circuit is correctly inserted in
the correct locations. Move the positive lead of the VOM to test point 6 (TP6). Make
sure that the power is ON. The voltage at TP6 should be close
to 0V. If your circuit passes this test, leave the VOM connected
and go to test 1 in the Dynamic Measurements Section. If your
circuit fails this test, turn the power OFF and check the IC. All
static tests must pass before proceeding to the Dynamic Tests or
the next section.
OUTPUT BIAS TEST
Figure 8
INPUT BIAS
V
Amps COM V/ Ω
TP8
Battery
If you do not have an audio generator, skip the following test and go directly to Section 2.
DYNAMIC MEASUREMENTS
Connect the VOM and audio generator to TP6 as shown in Figure 9.
Turn the power ON. Normally the AC gain is measured at a
frequency of 1 kilohertz (kHz). Your VOM, however, may not be
able to accurately read AC voltages at this frequency. It is
recommended, therefore, that this test be performed at 400Hz.
Set the audio generator at 400Hz and minimum voltage output.
Set your VOM to read an AC voltage of 1 volt at the output of your
Audio Amplifier (TP7). Slowly increase the output of the audio generator until the VOM reads 1 volt AC. Leave the audio at this
setting and move the positive lead of your VOM to TP6. Record
the AC voltage input to the amplifier here: Vin=___________
volts. You may have to change scales on your VOM for the most
accurate reading. Turn the power OFF. The AC voltage gain of
your Audio Amplifier is equal to the AC output voltage divided by
the AC input voltage, or 1/Vin. Your calculated AC Gain should
be approximately 100/180.
If an oscilloscope is not available, skip the following test and go directly to Section 2.
Figure 9
V
Amps COM V/ Ω
Output Adjust
TP8
TP8
Battery
10
μF
Generator
AC GAIN