Page 266
RECEIVER TROUBLESHOOTING GUIDE
Refer to the "Receiver Block Diagram"
(fold-out from
Page
For the following steps, you will need an input signal source
2671, which shows how signals flow through the receiver
to Connect to the AUX AUDIO socket on the rear panel.
circuits, as you go through the tests on the following pages.
You can obtain this input in either of two ways:
Each circuit board is outlined with a dashed line, and the
circuit functions are shown as solid blocks inside the 1.
Use
a 1 kHz signal from an audio generator.
outlines.
Thjs
troubleshooting guide is divided tnto the following five
tests: "Audio Output," "Product Detector," "Preamplifier,"
"IF Amplifier and AGC," "Crystal Filter," and "Front
End." When you get the correct result for a test, proceed to
the next one. If you do not get the correct result, the last
step will direct you to the proper part of the "Maintenance"
setion and will call your attention to some specific areas to
check. When you turn to the "Maintenance" section:
1. Refer to any applicable parts of the
"Troubleshooting Chart."
2.
Refer to the "Voltage Chart" and check the
voltages in your Transceiver at the areas
mentioned in the last step. (Also see "Voltage
and Continuity Checks," Page 272.)
3.
Check any questionable diodes and transistors.
See
Page 274.
4. Be sure each circuit is correctly wired and that
the correct parts are installed.
5. Read the "Circuit Description" and
smdy the
Schematic to better understand and analyze
your problem.
AUDIO OUTPUT
2.
Connect a separate speaker to the free end of
the 24" test cable (be sure to remove the 18
pF
disc capacitor) prepared earlier for front end
alignment. Then, to provide the signal, tap on
the cone of the speaker or scratch
it
with a
fingernail.
(
1
Connect your input signal source to the AUX AUDIO
socket on the rear panel. You should hear a sound
from your station speaker.
(
1 If you do not hear any sound from your station
speaker, proceed to "Receiver
IFIAudio Circuit
Board," Page 310. Check
0513 through Q518, IC502,
and the associated circuitry.
(
1
Disconnect the input signal source from the AUX
AUDIO socket. If necessary, disconnect the speaker
from the test cable and reconnect the 18
pF capacitor.
3.395
MHz
TEST SIGNAL
P.
307
In order to check the remaining stages in the receiver section
yw will need a 3.395 MHz test signal. You can make this
signal available as follows:
(
Turn the power ON.
(
)
Locate the 24" test cable
(
1
Turn the RF GAIN control fully clockwise.
&f
Lift the end of 100
S2
resistor R645 (on board
E),
that
forms
a
junction with the ferr~te bead. To identify
R645, refer to the X-ray view on the fold-out from
( )
Turn the AF GAIN control to rnid.range. Page 306.
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