Midland Radio SP-300 service manual Removing & Replacing the Main Board, To remove the Main Board

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MAXON SP-300 HAND HELD

REMOVING & REPLACING THE MAIN BOARD

To remove the Main Board:

1.Remove the Battery (Refer to Removing & Replac- ing the Battery).

2.Remove the PTT Assembly (Refer to Removing & Replacing the PTT Assembly).

3.Remove the Dust Cap (Refer to Removing & Replacing the Dust Cap).

4.Remove the Antenna & Control Knobs (Refer to Removing & Replacing the Antenna & Control Knobs).

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6

5.Remove the Back Cover (Refer to Removing & Replacing the Back Cover).

6.Insert a small straight (Flat Head) screwdriver blade between the Main Board and the radio chassis.

7.Gently pull backward with the screwdriver until the

Main Board has been unsnapped from the lower sec- tion of the chassis.

8.It may be necessary to pull the Main Board up a little more to gain easier handling for removal.

zCAUTION: If performing step 8, insure that the screwdriver is placed on the metal frame of the Main Board and not directly on the Main Board PCB. Damage to the Main Board and Microprocessor could occur.

9.Grip the Main Board near the indicated arrows as shown in Figure 9B.

10. Gently work the Main Board in an up & down motion and pull in the direction indicated by the arrow in Figure 9B.

zCAUTION: Do not use excess force when removing the Main Board from the chassis. Damage to the speaker connection could occur.

zNote: It is not necessary to remove the stud mount antenna jack from the radio.

11.Remove the Speaker wire connector from the Main Board connector.

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May 2001

Figure 9-Main Board Removal & Installation

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Figure 9A-Main Board Removal & Installation

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Figure 9B-Main Board Removal & Installation

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Contents Service Manual Table of Contents Board Layout Exploded View Specifications Temperature RangeGeneral Current ConsumptionDimensions WeightAdjacent Channel Power Frequency BandsReceiver Peak Deviation @ 1 kHz Nom. Dev +20dBRX Tone Demodulation Characteristics Features SP-300INTRODUCTIONBusy Channel Lockout VCO Lock Time Description of Controls DescriptionTheory of Operation Digital CircuitsRF Circuits RF Circuits PLL Synthesizer Squelch mute Circuit KHz Band Pass FilterNoise Detector Speaker Audio AmplifierMaintenance and Repair Removing & Replacing the Belt ClipRemoving the belt clip To replace the belt clipRemoving & Replacing the Battery To remove the batteryTo replace the battery To remove the PTT assemblyRemoving & Replacing the ACCES- Sory Connector Removing & Replacing the Antenna & Control KnobsTo replace the Back Cover Removing & Replacing the Back CoverTo remove the Back Cover Removing & Replacing the Main Board To remove the Main BoardTo replace the Main Board Removing & Replacing the Speaker Component ReplacementRemoving & Replacing the DAUGH- TER Boards Surface Mount Component Replacement Surface Mounted Integrated Circuit ReplacementCloning Alignment ProcedureProgramming RX VCO Test Equipment Setup S.G. @ 1kHz AudioAlignment Points Diagram TP1Troubleshooting Guide Symptoms Causes Counter MeasuresVoltage Charts Main CircuitReceive State Transmit State SP-300 Series UHF & VHF Digital Section Parts List REF# Description PART#-30- May SP-300 Series VHF RF Section Parts List REF # Description Replacement Modules-32- May -33- May SP-300 Series UHF RF Section Parts List -35- May -36- May -37- May Component Pinout KTA1504SY-39- May Base Diagram PIN Description VHF Power AMP UHF Power AMPVHF FRONT-END UHF FRONT-ENDVHF V.C.O UHF V.C.OFuse ACC-200 BatteryTcxo SP-300 Series VHF RF Schematic UHF RF Schematic -47- May Board Layout Top Main Board Assembly 416121B -49- May