Troubleshooting Guide; Notes For Advanced Users - Ramsey Electronics FR146 User Manual

FR146 TROUBLESHOOTING HINTS
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 (NE602, 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
NE602. If Q2 is defective or installed incorrectly, very little of the NE602'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.
SOME NOTES FOR ADVANCED USERS
Unlike Ramsey HF receivers and transmitters, the FR-series of VHF receivers
do not offer much PC board space or real need for customization or other
modifications. These receivers do what they are intended to do at the lowest
price that we are aware of for a tuneable VHF FM receiver with squelch, AFC
and generous audio output. Therefore, while we are certainly interested in
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