Midland Radio SP-300 service manual To replace the Main Board

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MAXON

SP-300 HAND HELD

To replace the Main Board

1.Reverse the steps taken to remove the Main Board.

2.When installing the Main Board into the chassis insure that the LED light guide is aligned properly.

3.When installing the Main Board into the chassis, place 2 fingers over the black rubber control knob dust covers to insure that the dust covers do not get pushed out of the appropriate seating position.

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Figure 9C-Main Board Removal & Installation

Page -18- May 2001

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Contents Service Manual Table of Contents Board Layout Exploded View Temperature Range SpecificationsGeneral Current ConsumptionWeight DimensionsAdjacent Channel Power Frequency BandsPeak Deviation @ 1 kHz Nom. Dev +20dB ReceiverRX Tone Demodulation Characteristics SP-300INTRODUCTION FeaturesBusy Channel Lockout VCO Lock Time Description Description of ControlsDigital Circuits Theory of OperationRF Circuits RF Circuits PLL Synthesizer KHz Band Pass Filter Squelch mute CircuitNoise Detector Speaker Audio AmplifierRemoving & Replacing the Belt Clip Maintenance and RepairRemoving the belt clip To replace the belt clipTo remove the battery Removing & Replacing the BatteryTo replace the battery To remove the PTT assemblyRemoving & Replacing the Antenna & Control Knobs Removing & Replacing the ACCES- Sory ConnectorRemoving & Replacing the Back Cover To remove the Back CoverTo replace the Back Cover To remove the Main Board Removing & Replacing the Main BoardTo replace the Main Board Component Replacement Removing & Replacing the DAUGH- TER BoardsRemoving & Replacing the Speaker Surface Mounted Integrated Circuit Replacement Surface Mount Component ReplacementAlignment Procedure ProgrammingCloning RX VCO S.G. @ 1kHz Audio Test Equipment SetupTP1 Alignment Points DiagramSymptoms Causes Counter Measures Troubleshooting GuideMain Circuit Voltage ChartsReceive State Transmit State REF# Description PART# SP-300 Series UHF & VHF Digital Section Parts List-30- May REF # Description Replacement Modules SP-300 Series VHF RF Section Parts List-32- May -33- May SP-300 Series UHF RF Section Parts List -35- May -36- May -37- May KTA1504SY Component Pinout-39- May Base Diagram PIN Description UHF Power AMP VHF Power AMPVHF FRONT-END UHF FRONT-ENDUHF V.C.O VHF V.C.OACC-200 Battery TcxoFuse SP-300 Series VHF RF Schematic UHF RF Schematic -47- May Board Layout Top Main Board Assembly 416121B -49- May