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FR10 TROUBLESHOOTING GUIDE
The Ramsey FR-series FM receivers are among our most widely-used
and popular kits. The circuit itself, assembly and use are "cut-and-dried."
If your receiver does not work, there is probably either an error in
assembly or a defective part. Following is some help in case you
experience difficulty.
Problem: Receiver completely "dead"- no sound at all.
Check the following:
First, the cable or plug adapter leading to speaker or phones!
Battery condition and battery wire polarity and soldering at S1.
Connections associated with U3, the LM386 audio output IC.
Problem: Receiver "hisses", but NO signals are heard, not even a signal
generator 2 inches away.
First, you need to verify that the local oscillator (SA602, L3, etc.) is
operating. Use another VHF receiver or a frequency counter to verify
oscillator operation. Next, make sure that the 10.24 MHz crystal oscillator
is running by tuning a general purpose HF ("shortwave") receiver to that
frequency. If either oscillator is not running, re-check correctness of parts
and solder joints associated with both oscillator circuits. Further signal-
path tracing may be necessary to find your problem.
Problem: Very weak signals
If Q1 is defective or incorrectly installed, very little signal energy will
reach the SA602. If Q2 is defective or installed incorrectly, very little of
the SA602's 10.7 MHz output is getting to the MC3359. Also, be sure that
L4 is peaked correctly.
Problem: Considerable frequency drift or shifting
First, make sure that L3 is soldered securely to the PC board. If you plan
to use the receiver "on the go", you may wish to secure the base of the
coil to the board with reinforcing glue. If the receiver drifts, check all
wiring and components associated with AFC Q3 and pin 11 of the
MC3359.
Problem: Squelch does not function
Re-check all connections and components associated with pins 10
through 16 of the MC3359. Check polarity of C27 and D2. C27 sets the
time constant for the squelch circuit.
FR-10 • 24
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