Ramsey Electronics COMPUTEMP CT255 Manuel d'instructions télécharger pdf (Page 21)

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.

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Ramsey Electronics COMPUTEMP CT255 Manuel d'instructions Page 21