Midland Radio SP-300 service manual Troubleshooting Guide, Symptoms Causes Counter Measures

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MAXON

SP-300 HAND HELD

TROUBLESHOOTING GUIDE

SYMPTOMS		CAUSES		COUNTER MEASURES

	1.	Complete discharge of battery (7.5v+/-10%)	1.	Replace battery
Unit does not Work	2. Fuse blown up (4a)		2.	Replace fuse
	3.	5v voltage source	3.	IC1 (5v+/-0.2v)
	1.	Low battery (lower than 5.6v)	1.	Replace or charge battery
Warning Tone & No Work	2. Pll error		2.	Check TCXO/ VCO/ PLL IC
	3.	Filtering error	3.	Check LPF (IC407)
	3.	Filtering error	3.	Check LPF (IC407)
	4 .EEPROM fail		4.	Re-programming
Defective RX Audio	1. No audio at speaker		1.	Replace speaker or check wire
	2.	Busy lamp (yellow Color) is o.k. but no Audio	2.	Check tone ch, audio amp(IC6) 300hz
				HPF (IC410) Sw IC (IC402B, IC411)
	1.	Defective ANT sw	1.	Check D5,D6
	2 .Defective front-end		2.	Check Q601
Bad RX Sensitivity	3. Defective dbm		3.	Check D9,T2,T3
(-10 to -60db)	4. IF IC		4.	Replace IC5
	5.	VCO level drop	5.	Rx VCO level>2dbm
	6.	Change of 1st local Frequency	6.	Retune TCXO
	1.	VCO frequency change or level drop	1.	Repair RX VCO
Defective RX	2. Defective voltage source		2.	Defective IF IC(IC5)
			3.	IC1,Q1,Q3
	1.	Defective 12.8 MHz TCXO	1.	Replace TCXO
PLL Error	2. Voltage source for Rx VCO/TX VCO		2. Check RX VCO/TX VCO
	3.	Defective PLL IC	3.	Replace IC2
Low TX power Output	1. APC		1.	Re-adjust RV1
	1. TX buffer		1.	Check Q16,17
No TX power	2. Power module		2.	Check Q501,502,503
	3. APC control		3.	Check Q22,D4
No modulation	1. Condenser mic		1.	Check mic
	2.	Sw IC & mic amp IC	2.	Check IC411, 410, 405, 401,404
No s.a.t.(tone)	1. 250 hz LPF		1.	Check IC406,407,411
	2.	RV403 adjustment	2.	Re-adjust RV403
No programming	1. Short protector VCC		1.	Check 6v on Q412, 413
			2.	Defective programming lead

Page -25- May 2001

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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 remove the Back Cover Removing & Replacing the Back CoverTo replace the Back Cover Removing & Replacing the Main Board To remove the Main BoardTo replace the Main Board Removing & Replacing the DAUGH- TER Boards Component ReplacementRemoving & Replacing the Speaker Surface Mount Component Replacement Surface Mounted Integrated Circuit ReplacementProgramming Alignment ProcedureCloning 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.OTcxo ACC-200 BatteryFuse SP-300 Series VHF RF Schematic UHF RF Schematic -47- May Board Layout Top Main Board Assembly 416121B -49- May