Design Brief #42
AM-FM Radio
“FM Ratio Detector”
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Follow the steps listed in the instruction manual to locate, place and solder all
components for the FM Ratio Detector circuit board. Make sure that your location of the
components matches the diagrams PRIOR to soldering anything into place. Misplacing a
component will result in the circuit board not working correctly and you will be required
to de-solder and replace any misplaced or damaged components.
Soldering must be accurate and clean.
Use the check off boxes on the diagrams to track your progress from component to
component.
“Static Measurements”
FM Voltage Test
For all measurements, connect your equipment Ground (Black Probe) to the circuit
ground at TP15.
1. Following the instructions on Page 34 of the instruction manual to complete the FM
Voltage test on the circuit you just soldered. (Make sure you switch the AM/FM
switch to FM position.)
a. What is the voltage of your battery? ______ volts.
b. What is the voltage at R25? ______ volts.
Transistor Current Test
Follow the instructions on Page 34 to determine the voltage at Q6.
1. What is the voltage at Q6? _______ volts.
2. Calculate the current (I) using the formula listed on page 34.
a. The current equals (I) ________ ma.
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