Motorola Gm3688 Service Manual 'link' -

Do not open the GM3688 without reading this first.

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| Symptom | Likely Cause | Service Manual Reference | |---------|--------------|---------------------------| | No TX, but RX works | PA driver Q301 (2SC5101) shorted | Section 4.2.3 | | Low sensitivity | Q101 LNA (BFG591) damaged | Section 4.1.1 | | Distorted audio on TX | Microphone preamp capacitor C411 leaky | Section 3.4 | | Channel knob erratic | Control head encoder (mechanical wear) | Section 6 – Encoder part # | | PLL unlocks on high freqs | VCO varactor diode D202 failing | Section 2.3 | Motorola Gm3688 Service Manual

To ensure optimal performance, the GM3688 radio requires periodic alignment and adjustment. The following procedures should be performed: Do not open the GM3688 without reading this first

Radio receives off-frequency (voices sound “Donald Duck”-like) or your transmitted carrier is 2-3 kHz off. Motorola Gm3688 Service Manual