Use an RF signal generator to inject a 45.1 MHz signal directly after the crystal filter. If audio demodulates successfully, the fault lies within the RF front-end stages or the mixer. If no audio is produced, the IF IC or its peripheral components are defective. Symptom: No Transmit Power Out
(Negative speaker return; do not ground this pin!). Pin 2: Microphone Audio (External mic input, nominal impedance).
Prevents the radio from over-deviating and bleeding into adjacent channels. 6. Accessing Official Documents Safely
Prevents the transmitter from over-deviating and causing adjacent-channel interference. Select -> Modulation Limit . motorola gm3688 service manual exclusive
To service the internal components, follow this specific sequence to avoid damaging the flex cables or the housing:
: Common display codes like "FAIL 01/82" usually indicate an internal checksum error or a failure in the EEPROM communication. Finding the Manual
Let’s be real for a second.
If you have just acquired the , keep these technician-approved tips in mind:
The filtered RF signal mixes with the Local Oscillator (LO) frequency generated by the Synthesizer to produce a 45.1 MHz First Intermediate Frequency (IF).
Traces the microphone input through the modulator, power amplifier (PA) stage, and low-pass filter to the antenna switch. Use an RF signal generator to inject a 45
: Using Motorola’s Customer Programming Software (CPS) and a Tuner application to calibrate frequency, power, and modulation. Disassembly
Measure the RSSI voltage at the IF IC test point. A normal RSSI but bad audio points to a faulty audio amplifier circuit (U401). A low RSSI points to a blown front-end RF transistor (Q101) or misaligned varactor filters. Problem 3: Low or No Transmit Power