EFJohnson 7780 service manual Audio Amplifier IC104-IC106, Receive and Transmit Data Processing

Page 72

CIRCUIT DESCRIPTION

Table 4-1 Microprocessor IC306 Pin Descriptions (Continued)

Pin

Port Name

Input or

Description

Active High

Name

Output

or Low

 

 

 

 

 

 

 

93

S5C

Output

RF 5C supply control signal

High

94

-

-

-

-

 

 

 

 

 

95

SN_TR

Output

SMARTNET circuit control signal (H=SMARTNET Tx Data)

High

 

 

 

 

 

96

EEPCS

Output

EEPROM chip select signal

-

 

 

 

 

 

97

XTXD

Output

Programming data out

-

 

 

 

 

 

98

XRXD

Input

Programming data in

-

 

 

 

 

 

99

PTTIN

Input

PTT switch

Low

 

 

 

 

 

100

-

-

-

-

4.6.2 EXPANDER (IC208)

From this filter the signal is fed to pin 7 of the expander in IC208. When companding is enabled by a low input on the PT input of IC208, this stage provides 1:2 expansion of the audio signal to remove the 2:1 compression that occurred when it was transmitted. This compression and then expansion reduces the amount of noise present in the audio signal. When the PT input is high, companding is disabled and the signal if fed through IC208 without expansion. NOTE: Companding is not currently used with this radio.

The audio signal is fed out of IC208 on pin 15 and then fed to audio mute gate IC103. This gate is controlled by the RMUTE output (pin 84) of the microprocessor. The audio is also muted by the audio amplifier as described in the information which follows.

4.6.3 AUDIO AMPLIFIER (IC104-IC106)

From gate IC103, the audio signal is fed to volume control R117 which sets the input level to the audio amplifiers. Also applied at this point are the DTMF and beep tones. Muting of the DTMF tones is provided by Q101 which is controlled by the DTMFMT output (pin 82) of the microprocessor. The beep tones are synthesized by the BEEP output (pin 53) of the microprocessor.

The input level to the audio amplifiers is also controlled by Q112 which lowers the input level by grounding R168. Both the NPSPAC and W/B (wide/ narrow band) lines control Q112. Resistor R168 is grounded only in the narrow band/non-NPSPAC mode (see preceding information for line levels).

With normal operation when the internal speaker is used, IC105 and IC106 provide the required amplifi- cation. However, when an external speaker-micro- phone is connected to pin 1 of the accessory jack (a load of approximately 1k ohm or less), Q102 and

Q105 turn on and Q109 turns off. This disables IC105 and IC106, and enables IC104.

The supply voltage to all three audio amplifier stages is controlled by Q106 and Q107. When the audio is muted such as when no tones are sounding or no message is being received, the AMUT output of the microprocessor (pin 85) is low. This turns off both Q106 and Q107 and removes supply voltage from the audio amplifiers. This helps conserve battery power. The receive audio signal is also muted by gate IC103 as previously described.

4.7RECEIVE AND TRANSMIT DATA PROCESSING

4.7.1RECEIVE DATA FILTER/DETECTOR (IC102A/B, IC107A/B)

The receive data (and audio) signal (DET) from the IF board is also routed to the receive data filter formed by IC102B and IC102A. This is a low-pass filter which attenuates voice and other harmonic frequencies above the data band.

The passband of this filter is controlled by the BWC signal applied to Q103. When digital Call Guard data or a low-frequency Call Guard tone is being detected, the BWC signal is high which turns on Q103. The cut-off frequency of the filter is then approximately 150 Hz. Then when a high-frequency Call Guard tone is received, Q103 turns off and the

November 1999

 

Part No. 001-7780-500

4-8

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Contents 7780 Page Page Table of Contents Table of Contents CONT’D List of Tables List of FiguresGeneral Information Scope of Manual Equipment DescriptionAccessories Factory Customer ServicePart Number Breakdown Transceiver IdentificationAccessories AccessoryToll-Free 800 Factory ReturnsReplacement Parts Internet Home Intrinsically Safe InformationDefinitions Temperature Code T3C Possible Ignition SourcesIntrinsically Safe and Nonincendive Ratings Classification of Hazardous Areas and AtmospheresAccessing PC Boards Material ClassificationTypical Hazard Group Class Area ClassificationRemoving RF Unit Removing Logic UnitSpecifications GeneralFeatures Transceiver OperationControls and Display TX Indicator Red Indicates when the transmitter is keyed Low-Battery Indicator AmberDisplay Front Panel Keys Full Keypad ModelDisplay Turning Power on and Setting Volume Option SwitchesGeneral Operation BacklightOption Switch Functions Function ConvSee Tone ENABLE/DISABLE ScanningConventional and SMARTNET/ Smartzone Operation Conventional Features Display Mode SelectionMonitoring Before Transmitting Monitor Mode Busy Channel LockoutCall Guard Squelch Penalty Timer Conversation TimerPower Output Select Conventional Mode ScanningPriority Channel Sampling DTMF/ANI Signaling Standard Conventional CallsSMARTNET/SMARTZONE Features Viewing Unit IDStandard Group Calls Enhanced Private Conversation CallsTransceiver Operation Private Conversation II Calls Telephone Calls Call Alert Emergency Alarm and Call MessagingSending Status Conditions Failsoft Operation SMARTNET/SMARTZONE ScanningDynamic Regrouping Supervisory Tones Keypad Programming Menu DescriptionZone Change Parameter Channel Change Parameter System ParametersChannel Parameters Programming Setup Pctrunk Software InstallationTransceiver Programming Computer DescriptionConnecting RPI to Computer and Transceiver Starting and ExitingProgramming File Types Help FilesScreen Pop-Up Buttons and File Size Indicator Programming ProcedureFile Size Indication Creating and Displaying SystemsMenu Commands Menu BarRadio Type Menu Download Menu Upload MenuSystems Menu Window MenuDefaults RADIO-WIDE Parameter ScreensBand ZonesRadio Wide Scan List Radio-Wide Scan List ScreenModify List Screen Assign Function ButtonsRADIO-WIDE Conventional Screen RADIO-WIDE SMARTNET/SMARTZONE ScreenFull Spectrum CC Scan Hot DtmfAdjustable Parameters RADIO-WIDE Portable Options ScreenProgramming Conventional Systems and Channels Conventional System General ScreenTimers Conventional System Modify Scan List ScreenKeypad Editing Scan List ButtonScan Timers Setting UP Conventional ChannelsPriority Channel Selection Conventional Channel Screen Parameters Selected ChannelTransmit Power SignalingChannel Type Tx Time-OutRestricted Access Time-Out TimerISW Delay Time Splinter ChannelsSMARTNET/SMARTZONE System Other ID’S Screen SMARTNET/SMARTZONE System Phone Interconnect ScreenPhone Interconnect Private CallSMARTNET/SMARTZONE System Emergency Settings Screen Emergency AlarmSMARTNET/SMARTZONE System Talk Groups Screen Failsoft ChannelSMARTNET/SMARTZONE System Lists Screens Trunking Phone List ScreenMessage Aliasing Screen Announcement Groups Screen Control Channels ScreenTrunking Call List Screen Setting UP SMARTNET/SMART- Zone Channels Status Aliasing ScreenSMARTNET/SMARTZONE Channel Screen Parameters SMARTNET/SmartZone Channel Screen Other Screen ParametersCall Guard CTCSS/DCS Codes and Tones Recommended Tone Call Guard Codes FreqMHz Channels MHz Channels MHz Channels MHz Channels MHz Channels MHz Channels Power Switching and Regulation Power SwitchingCircuit Description Synthesizer DescriptionVCO and Tcxo Modulation Synthesizer Chip IC1Charge Pump Q1, Q2, Loop Filter Receiver Circuit Description RF Amplifier Q1, First Mixer Q2If Amplifier Q2, LIMITER/DETECTOR IC3 Antenna Switch and LOW-PASS Filter Squelch Circuit IC4A/B, IC5ATransmitter Description Amplifier Q9, Driver Q8Control Logic and Display Receive Audio ProcessingMicroprocessor IC306 Pin Descriptions Pin Port Name Input or Description Active High OutputHvfulswlrq Audio Amplifier IC104-IC106 Receive and Transmit Data ProcessingReceive Data FILTER/DETECTOR IC102A/B, IC107A/B Transmit Data Filter IC206B/ IC206A Transmit Audio ProcessingLOW-PASS Filter IC205A/B Smartnet Data ProcessingBattery Pack and Charger Information Battery PackPower Setting Operating Time Function Fahrenheit CelsiusBattery Pack and Charger Information Alignment Procedure and Performance Tests Test SetupTune Software Hqhudo Mm/3/32 Mm/1/8 Phone JackPreliminary Setup Main Pctune ScreenTransmit Frequency and Power Transmit Power Adjustment ScreenHigh Power Level = 3.0 watts Low Power Level = 1.0 watt Modulation BalanceSquelch Adjust Rssi AdjustAudio Deviation Data DeviationPerformance Tests Receiver Performance TestsPower Output Transmitter Performance TestsTransmit Frequency Transmit ModulationThis page intentionally left blank Parts List Display AssemblyChassis Parts Ref No DescriptionKEY Assembly Display AssemblyIf Assembly KEY AssemblyIf Assembly PLL Assembly RF UnitRF Unit NJM2904V-TE1 IC RF Unit Logic Unit Logic Unit TDA7233D IC Logic Unit 200K ERJ3GE MP35 MP18 MP25 KEY Front Panel EP2EP1 MP32 MP33 MP27 MP34 MP28 MP29 MP23 MP22 MP30 MP24 MP26 MP18 Schematic Diagrams and Component Layouts PLL Board TOP ViewPLL Board Bottom View If Board TOP View If Board Bottom ViewTransceiver Block Diagram RF UnitRF Board TOP View MICRF Board Schematic If AMPLogic Board TOP View HD1Logic Board Schematic Receive Audio ProcessingDisplay Board Bottom View GND KEYR3 KEYR2 KEYR1 KEYR0 KEYS3 KEYS2 KEYS1 KEYS0 GNDDisplay Board Schematic DS3 DS4 DS5KEY Board Front View KEY Board Back ViewKEY Board Schematic S S R R R RScan HC2 HC7 HC8 HC3 Schematic Diagrams and Component Layouts
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