Motorola Gm3688 Service | Manual Top

Do not perform without proper test equipment. Default service password is often blank or MOTOROLA.

RF Alignment Procedure (UHF Example):

| Step | Alignment Item | Condition | Target | | :--- | :--- | :--- | :--- | | 1 | Reference Oscillator | Frequency counter at TP101 (internal) | ± 150 Hz @ 25°C | | 2 | Transmit Power – Low | 12.5W setting | ± 1W | | 3 | Transmit Power – High | 45W setting (UHF) | ± 2W | | 4 | TX Deviation – Low | 1 kHz tone @ 60% rated deviation | 2.5 kHz (12.5 kHz channel) | | 5 | RX Front End | Tune bandpass filters for max SINAD | < 0.35 µV for 12 dB SINAD | motorola gm3688 service manual top

The Motorola GM3688 is a mobile radio designed for the Professional Commercial Radio (PCR) market. It is part of the GM360/GM380 family but features a different control head design. This manual covers:

Prerequisite: Connect the radio to a stable 13.2V DC power supply and a PC running the "Tuner" application. Connect the RF cable to a dummy load or test set via the antenna port. Do not perform without proper test equipment

| Category | Item | | :--- | :--- | | Programming | Motorola CPS (Customer Programming Software) R06.12.05 or later. | | Cable | Ribless programming cable (aftermarket HKN6184 clone) – uses USB or Serial. | | Service Monitor | Aeroflex IFR 2975, HP 8920B, or similar (for alignment). | | Alignment Cable | Motorola RIB to radio 2-pin mic connector (GPN: 3080369B71). | | Multimeter | True RMS for audio/DC measurements. |

To service the GM3688, the following equipment is required: The GM3688 uses digital potentiometers controlled via the

The GM3688 uses digital potentiometers controlled via the CPS (Computer Programming Software). The service manual tells you exactly which soft-pot adjusts the TX audio deviation. Pro tip: Over-deviating above 5 kHz will cause distortion on repeaters. The manual provides the 60% deviation limit (3 kHz) for optimal talk power.