Maxon Telecom SM-2000 service manual Surface Mount Component Replacement

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MAXON SM-2000 MOBILE

COMPONENT REPLACEMENT

SURFACE MOUNT COMPONENT REPLACEMENT

1.“Tin” one terminal end of the new component and the corresponding pad of the PCB. Use as little solder as possible.

2.Place the component on the PCB pads, observing proper polarity for capacitors, diodes, transistors, etc.

3.Simultaneously touch the “tinned” terminal end and the “tinned” pad with the soldering iron. Slightly press the component down on the board as the solder liquefies. Solder all terminals, allowing the component time to cool between each application of heat. Do not apply heat for an excessive length of time and do not use excessive solder.

With a hot-air system, apply hot air until all “tinned” areas are melted and the component is seated in place. It may be necessary to slightly press the component down on the board. Touch-up the soldered connections with a standard soldering iron if needed. Do not use excessive solder.

CAUTION: Some chemicals may damage the internal and external plastic parts of the radio.

4.Allow the component and the board to cool and then remove all flux from the area using alcohol or another approved flux remover.

SURFACE MOUNTED INTEGRATED CIRCUIT REPLACEMENT

Soldering and de-soldering techniques of the surface mounted IC’s are similar to the above outlined procedures for the surface mounted chip components. Use extreme care and observe static precautions when removing or replacing the defective (or suspect) IC’s. This will prevent any damage to the printed circuit board or the surrounding circuitry.

The hot-air soldering system is the best method of replacing surface mount IC’s. The IC’s can easily be removed and installed using the hot-air system. See the manufacturer’s instructions for complete details on tip selection and other operating instructions unique to your system.

If a hot-air system is not available, the service technician may wish to clip the pins near the body of the defective IC and remove it. The pins can then be removed from the PCB with a standard soldering iron and tweezers, and the new IC installed following the Surface Mount Component Replacement procedures. it may not be necessary to “tin” all (or any) of the IC pins before the installation process.

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December 98

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Contents SM-2000 Page Maxon SM-2000 Mobile Table of ContentsPCB Layouts Schematics and Block DiagramsSM-2000 Exploded View Transceiver Nominal Performance SpecificationsGeneral Band Operational BandwidthTransmitter Specfications SUB Audible Tones DCS TX Tone Modulation CharacteristicsReceiver Accessories RX Tone Demodulation CharacteristicsSubaudible tones CTCSS/DCS Reliability AnalysisIntroduction Check the carton carefully for the following items Unpacking InformationGeneral Description Description of Controls Description of ControlsSM-2000 Rear Panel Digital Circuitry Theory of OperationCTCSS/DCS Decode Circuits CTCSS/DCS Encoder CircuitEeprom PLL RF Section SM-2150/VHF TX VCO RX VCOPrescaler Out of Lock DetectorReceiver RF AmplifierLow Pass Filter Receiver Audio CircuitAudio Amplifier Noise Detect Circuit SQ BoardUHF Transmitter RF Section SM-2450/UHFFrequency Synthesizer Circuit First Mixer Voltage Controlled Oscillator CircuitSecond Oscillator- Mixer- Limiter and FM Detector Squelch Noise Band Pass Filter Squelch Mute CircuitNoise Detector Speaker Audio AmplifierTransmit Tests Test SetupPLL Alignment SM-2150/VHF Alignment ProcedureReceiver Alignment RF Discriminator TuningAutomatic Power Adjustment Squelch AdjustmentModulation Deviation Adjustment CTCSS/DCS Deviation AdjustmentAlignment Points Diagram SM-2150/VHF SM-2450/UHF Alignment Procedure Page-28 December ∙ Note Release the PTT button when changing channels Page-30 December Alignment Points Diagram SM-2450/UHF Surface Mount Components Component ReplacementSurface Mount Removal Surface Mounted Integrated Circuit Replacement Surface Mount Component ReplacementREF # Description Parts List Common to SM-2000Digital Parts Common on Both VHF & UHF Digital Section REF # Description FRONT-END PCB Assembly Main Board Parts Band ChartPage-38 December Page-39 December Page-40 December Page-41 December SM-2450A UHF Band SM-2450C UHF Band SM-2450D UHF Band SM-2450E UHF Band Band ChartPage-44 December Page-45 December Page-46 December Page-47 December Component Pinout Page-49 December Page-50 December IC409 Voltage Charts SM-2150/VHFPage-52 December Transistor Voltage Chart Voltage Charts SM-2450/UHF IC404 Page-56 December Status Indications & Audible Tones Trouble Shooting Chart SM-2000Page-58 December MMBV109 Replacement Module SchematicsMA-4472 Microphone Schematic Page-61- December Page-62- December Page-63- December Page-64- December SM-2000 Control Head SW5Page-66 December SM-2150/VHF Main Board AssyFront SM-2450/UHF Main Board AssySM-2000 SM-2150/VHF Exploded View Parts List Intentionally Left Blank