Maxon Telecom SM-2000 service manual ∙ Note Release the PTT button when changing channels

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MAXON SM-2000 MOBILE

SM-2450/UHF ALIGNMENT PROCEDURE

Automatic Power Adjustment

NOTE: Continuous transmit periods longer than 5 minutes are to be avoided.

1.Connect the antenna output to an RF power meter or service monitor.

2.Set the PTT switch to the ON position.

3.Adjust the Variable resistor RV104 to give the appropriate transmit power. Nominally this is 25watts .

4.Set the PTT switch to the OFF position.

5.Select a channel programmed to low transmit power.

6.Set PTT to ON and adjust RV105 for desired low power .

7.Set PTT to OFF.

CTCSS/DCS Deviation Adjustment

NOTE: The following adjustment should be preset with factory alignment. If an adjustment must be made the following procedures must be followed:

1.Program the radio with a 67.0Hz tone on one channel and 250.3Hz on another channel.

2.Connect a power meter and modulation meter to the radio antenna jack.

3.Adjust RV101 to the center of its adjustment.

Note: Release the PTT button when changing channels.

4.Alternately select the channel with tone 250.3Hz and the channel with tone 67Hz . Key up and note the level for each. If necessary, adjust RV101 until a balance occurs between tone 250.3Hz and tone 67Hz .

Note:This adjustment also sets DCS balance even if a DCS tone is not programmed at this time.

5.Select tone 250.3Hz or tone 67Hz and adjust RV403 for the tone level, typically between 500Hz to 1kHz.

6.Release the PTT button.

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December 98

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Contents SM-2000 Page Maxon SM-2000 Mobile Table of ContentsSchematics and Block Diagrams PCB LayoutsSM-2000 Exploded View Specifications Transceiver Nominal PerformanceGeneral Operational Bandwidth BandTransmitter Specfications TX Tone Modulation Characteristics SUB Audible Tones DCSReceiver 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 BoardRF Section SM-2450/UHF UHF TransmitterFrequency Synthesizer Circuit Voltage Controlled Oscillator Circuit First MixerSecond 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 Component Replacement Surface Mount ComponentsSurface 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