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Motorola EP450 service manual If IC

Models: EP450

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2-2	Theory Of Operation: Major Assemblies

The IFIC is a low-voltage monolithic FM IF system incorporating a mixer/oscillator, two limiting IF amplifiers, quadrature detector, logarithmic received signal strength indicator (RSSI), voltage regulator and audio, and RSSI Op Amps. The second LO frequency, 44.395 MHz, is determined by a crystal oscillator. The second mixer converts the 44.85 MHz high IF frequency to 455 kHz.

Additional IF selectivity is provided by two ceramic filters. The first ceramic filter is a 4-pole filter used between the second mixer and IF amp. The second ceramic filter is a 6-pole filter and is used between the IF amp and the limiter input. For the second ceramic filter, a wider filter is used for 20/25 kHz channel spacing, and a narrower filter is used for 12.5 kHz channels.

A ceramic resonator provides phases vs. frequency characteristic required by the quadrature detector, with 90 degree phase shift occurring at 455 kHz. The output of the IFIC is the recovered audio signal which is fed to the audio IC for amplification and signal conditioning. The output of the audio IC is injecting into the audio PA which drives the 24 Ohm speaker.

2.2.2Transmitter

•When the radio is transmitting, microphone audio is passed through the audio IC, where pre- emphasis and low-pass (splatter) filtering are done. The output of the audio IC is used to modu- late the TX VCO, which creates the modulated carrier. The modulated carrier is then amplified by the pre-driver and power amplifier circuit, which transmits the signal under dynamic power control

Ref. Osc.

Frac N		Tx VCO	Tx	PA
		Tx VCO	Predriver	Module
		Circuit	Predriver	Module
		Circuit	Tx Out
			Tx Out
	Loop		VCOBIC
	Filter		VCOBIC	Power
	Filter		Rx Out
			Rx Out
				Cntr
Mod		Rx VCO
Mod		Circuit
		Circuit
Audio PA				T/R
Audio PA				Switch
				Switch

Spkr

Audio IC

Mic

	BW_SEL				Filter
Recovered Audio	BW_SEL				Preselector
Recovered Audio					Preselector
Ceramic	6G	6E	Cer Fltr		Rx
Ceramic		Switching	4E		Rx
Resonator		Switching	4E		LNA
Resonator					LNA
			IF Amp	Crystal
Demodulator				Filter	Image
					Image
					Filter
					Filter
					Mixer

RSSI

IF IC

Harmonic

Filter

Figure 2-2. Transceiver Block Diagram

December 3, 2003

HKLN4215A

Image 19

Motorola EP450 service manual If IC

Contents

EP450 HKLN4215A Document Copyrights Product Safety and RF Exposure ComplianceForeword Computer Software CopyrightsTable of Contents Display Model Disassembly and Re-assembly Troubleshooting Tables Appendix a AccessoriesList of Figures 13. Microphone and Speaker Wires Re-assembly Related Publications List of TablesRadio Model Information Model Charts and Test SpecificationsModel Description Model Chart for VHF 146-174 MHz EP450, VHF, 146-174 MHzReceiver VHF Test SpecificationsGeneral TransmitterModel Chart for UHF 403-440 MHz EP450, UHF, 403-440 MHz Model Chart for UHF 438-470 MHz EP450, UHF, 438-470 MHz Model Chart for UHF 465-495 MHz EP450, UHF, 465-495 MHz LAH65SDH9AA4N UHF Test SpecificationsMIL-STD MIL StandardsIntroduction Theory Of OperationMajor Assemblies If IC Motorola Part No Description Characteristics Application Test Equipment, Service Aids, and Service ToolsTest Equipment Motorola Part Description Application Service AidsTest Equipment, Service Aids, and Service Tools Service Aids 5mm Programming/Test CablePerformance Checks Power-Up Self TestGeneral Service Monitor Test Set Power Supply RF Test ModeNo. of BKC No. Description Function BeepsVHF R2 UHF R1 UHF R2 UHF R3 Test Name Communications Analyzer Radio Test Set Comments Test ModePerformance Checks RF Test Mode CPS Programming Setup Radio Alignment ProceduresRadio Tuning Setup Radio Tuning SetupTransmitter Alignment Options Initial Test Equipment Control SettingsReference Oscillator Warp Under Tx Align menu, select Reference Oscillator Warp Figure Modulation Balance AttenuationTransmit Power Window High Power Transmit Power TuningTo Perform Transmit Low Power Tuning, do the following To Perform Transmit High Power Tuning, do the followingVCO Attenuation When using test box RLN4460VCO Attenuation 25 kHz Under the Tx Align menu, select VCO Attenuation 20 kHz VCO Attenuation 12.5 kHzVCO Attenuation 20 kHz Under the Tx Align menu, select VCO Attenuation 12.5 kHzUnder Tx Align, select Dtmf Deviation Figure Dtmf Deviation TuningMDC-1200 Deviation Tuning Receiver TuningUnder the Tx Align, select MDC-1200 Signaling Figure Perform the rated volume tuning procedure as follows Rated Volume TuningManual Squelch Tuning Squelch TuningAuto Tune Rssi System Level TuningRadio-to-Radio Cloning Rssi Display TuningUnder the Rx Align menu, select Rssi Display Tuning Utilities12. Side Button Locations ProcedureRadio Alignment Procedures Radio-to-Radio Cloning Cleaning External Plastic Surfaces Display Model Disassembly and Re-assemblyPreventive Maintenance Cleaning ProceduresSafe Handling of Cmos and Ldmos Devices Cleaning Internal Circuit Boards and ComponentsFront Cover From Chassis Disassembly Radio Disassembly DetailedDisassembling and Re-assembling the Radio General Antenna and Knob Removal Keyboard Flex Connection Speaker and Microphone Disassembly Dust Cover DisassemblyKeyboard Removal PTT DisassemblyAudio jack shroud can be removed from the main board Chassis DisassemblyDust Cover Re-assembly Radio Re-assembly DetailedMicrophone and Speaker Re-assembly 12. Microphone Re-assembly 14. Keypad Re-assembly Keypad and LCD/Keyboard Re-assemblyChassis Assembly/Re-assembly Keyboard Retainer Re-assembly17. Main Board onto Chassis Re-assembly Chassis and Front Cover Re-assembly18. Microphone and Speaker Wires Re-assembly 20. Fastening the Chassis PTT Re-assembly1 EP450 Display Exploded View and Parts List Mechanical View and Parts ListMotorola Motorola Part Description NumberDecember 3 Introduction Non-Display Model Disassembly and Re-assemblySafe Handling of Cmos and Ldmos Devices Disassembling and Re-assembling the Radio General Antenna and Knob Removal Speaker Connector Shroud Microphone Speaker and Microphone Disassembly Removal of Main Board from Chassis Chassis DisassemblyDust Cap Re-assembly 11. Speaker Re-assembly 12. Installation of Main Board onto Chassis 13. Microphone and Speaker Wires Re-assembly 15. PTT Re-assembly 16. EP450 Non-Display Radio Exploded View 1 EP450 Non-Display Exploded View and Parts List14Mechanical View and Parts List Error Code Possible Causes Corrective Action Troubleshooting TablesPower-Up Error Codes Operational Error CodesTroubleshooting Table for Receiver Troubleshooting Table for Transmitter Troubleshooting Tables Troubleshooting Table for Transmitter Chargers Appendix a AccessoriesCarrying Accessories AntennasHeadsets Audio AccessoriesManuals Remote Speaker MicrophonesAccessories Scope of Manual Appendix B Warranty, Service Support, and Replacement PartsWarranty Replacement Parts OrderingFax Orders Motorola OnlineMail Orders Telephone OrdersMotorola de Mexico Service Center Motorola de Colombia Service CenterTechnical Support Appendix B-4 Term Definition Glossary of TermsReset