Ramsey Electronics manual FR146 TROUBLESHOOTING HINTS, Some Notes For Advanced Users

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:

ˆFirst, the cable or plug adapter leading to speaker or phones!

ˆBattery condition and battery wire polarity and soldering at S1.

ˆConnections 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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