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FR6 • 21
suited for Ramsey amateur kit boards is Radio Shack No. 270-253A. This
metal utility cabinet can accommodate both a receiver and transmitter board,
plus speaker, with room for various refinements you might like to add.
FR6 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.