EFJohnson 761X, 764X service manual VHF Adjustments, Preliminary Setup, PLL Adjustment VHF Models

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ADJUSTMENT PROCEDURE

VHF ADJUSTMENTS

in the upper part of the screen is for the currently selected channel.

5.To move the cursor between the parameters on the left side of the bar graph, press the ↑ ↓ arrow keys. To change a parameter, press the , PgUp/PgDn, backspace, or spacebar keys. Refer to the individual adjustment descriptions for more information on the

functions performed using this screen.

6.1.5REPROGRAMMING IF EEPROM IS RE- PLACED OR ERROR OCCURS

When EEPROM IC3 is replaced or if the trans- ceiver displays an error message and beeps, the fol- lowing operation must be performed before making any adjustments.

1.Using the programming software, read (download) the data programmed in an exact same version of the transceiver. Refer to Section 4.4.4 for more information on reading data.

2.Select the MODEL menu and press the down arrow ( ) key. Type “RESERVE” and press (ENTER).

The “Reserved” indicator should begin flashing in the upper right corner of the screen.

3.Connect the computer to the transceiver that had the EEPROM replaced or is displaying the error (see Figure 4-1). Write the current data to that transceiver.

6.2 PRELIMINARY SETUP

1.Preprogram the transceiver with test channels as described in Section 6.1.2.

2.Connect the computer test setup using the test cable described in Sections 6.1.3 and 6.1.4. Start the program as described.

3.Connect a DC power supply and a 50-ohm, 50-watt antenna load to the transceiver (see Section 6.1.1).

VHF ADJUSTMENTS

6.3 PLL ADJUSTMENT (VHF MODELS)

1.Remove the bottom cover by removing four screws. Connect a DC voltmeter to check point CP1 shown in Figure 6-4.

2.Select the channel on the high end of the band

(Test Ch. 1 - 174.050 MHz). This is done by press- ing the ↑ ↓ arrow keys to highlight “Memory CH” and then pressing the adjust keys (/→, PgUp/

PgDn, or spacebar/backspace) to select the channel.

3.Key the transmitter using the switch on the test cable and the meter reading should be 4.3 volts. If this voltage is significantly different, adjust L14 (it may be necessary to remove the VCO shield).

4.Unkey the transmitter and the meter reading in the receive mode should be 3.3 – 4.3 volts.

5.Select the channel on the low end of the band (Test Ch. 2 - 146.050 MHz). The meter reading should be 0.9 – 1.9 volt in both the transmit and receive modes. Replace the bottom cover.

6.4TRANSMITTER ADJUSTMENTS (VHF MODELS)

6.4.1 REFERENCE FREQUENCY

1.Select the channel on the high end of the band (Test Ch. 1 - 174.050 MHz).

2.Scroll down to “TXF SET” on the screen and press (Enter). Monitor the transmit signal with a fre- quency counter and key the transmitter using the test cable switch.

3.Adjust for the displayed frequency by pressing the computer adjust keys. Unkey the transmitter.

November 1998

 

Part No. 001-7600-001

6-4

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Contents 761x VHF 764x UHF Conventional Mobile Conventional FM TWO-WAY Radio Table of Contents Table of Contents CONT’D Schematic Diagrams and Component Layouts General Information Factory Returns 75xx AccessoriesAccessory Toll-Free 800Internet Home Replacement PartsThis page intentionally left blank General VHF and 7640 UHF Mobile SpecificationsGeneral Information Transceiver Installation Installation and DisassemblyCable Installation Installing Mounting BracketInstalling Microphone Hanger Power Cable InstallationAccessory Cable Installation Power Cable FusesChanging 20-Ampere Power Cable Fuses Using AN External SpeakerRemove shield E Transceiver DisassemblyRemoving PC Board 2 2-TONE Programming 2-TONE/5-TONE Module InstallationInstallation Procedure Setting 5-Tone DeviationInstallation and Disassembly Operation FeaturesBasic Operation Controls and DisplayTransceiver Back Panel Direct Selection The F1-F4 Receiving and Placing Calls Function Key Label Description Section No TIME-OUT TimerProgrammable Functions Option Key Programmable FunctionsChannel Select Monitor Mode SelectOutput Power Select Call Guard Tone SelectChannel Scan Priority Channel Sampling Programming Software Programming SetupSection Programming Programming CablesFile Menu Starting the ProgramSpecial Keys and Functions Menu FlowModel Menu Screen MenuProgram Menu Print MenuParameter Description Bank Select Setup MenuMemory Channel Screen Description LMR Models Rx/Tx TimerCh Atr FrequencyTone Auto ResetLockout ScanKey Description Key and Display Assign Screen DescriptionKey Description Label Bank/Free RF PowerDtmf Autodial Screen Description SelectionParameter Description Continuous Tone Screen DescriptionScan Function Screen Description Auto CH Stop Timer2-Tone Code Channel Screen Description ResumeStun EXO TimerTimer Auto Tx Auto TxCommon Screen Description Expert Screen Description Unique PMR Screens Unique PMR European ScreensCloning Programming ONE Transceiver with Another Memory Channel Screen PMR Models This page intentionally left blank VHF Receiver Circuit VHF 7610 Circuit DescriptionReceiver Mute Circuit Audio Amplifier CircuitModulation Circuit Power Amplifier ModuleVHF Transmitter Circuit Microphone Amplifier CircuitPLL Circuit APC CircuitVHF PLL Circuit Pin Port Description VHF IC PIN DescriptionsLine Description Pin Port Description Name VHF I/O Expander IC5 Main UnitPin VHF Port Expander IC11 Main UnitUHF Receiver Circuit UHF 7640 Circuit DescriptionSecond if System IC1 UHF UHF Transmitter Circuit UHF PLL Circuit PLL Circuit UHFUHF CPU IC1 Port Allocation UHF Power SupplyUHF Port Expander IC13 Main Unit UHF I/O Expander IC12 Main UnitEquipment Grade and Range Adjustment ProcedureTest Setup Suggested Test EquipmentTest Cable Test ChannelsUHF Test Frequencies COMPUTER-AIDED TuningVHF Test Frequencies PLL Adjustment VHF Models VHF AdjustmentsVHF Adjustments Preliminary SetupFM Deviation Adjust VHF Adjustments CONT’DOutput Power Adjust Squelch Adjust Dtcs Waveform AdjustReceiver Adjustments VHF Models Bandpass Filter AdjustBeep Tone Level Beep Tone Level AdjustmentTransmitter Adjustments UHF Models UHF AdjustmentsPLL Adjustment UHF Models UHF Adjustment Points UHF Adjustments CONT’DUHF Adjustments CONT’D Receiver Adjustments UHF Models Æçìíýõ9+ôý0$,1ý81,7 Parts ListÍäç HUDPLFý&ìçíåý-%ýì+ýìíë.ð7ð$ Íëëðêäíçðíçí Íäæ Ìää HUDPLFý&ìçíåý-%ýì&ýìíé.7ð1 Íëëðêäíçðçìé Ëíí Ëäí HUDPLFý&ìçíåý-%ýìýìíê.ð7ð$ Íëëðêäíçðíçê Ëäì RLOý0/ìçíå$ýì5í.ð7 Íëëðêäíçðçèç 03ì Ýìäëëý9&2ýFDVH 5íéé 5HVý5-ê*-ýìííý9ýõìíýRKPô Íëëðêäíçðìêå 5íéè 5ìèé 5HVý5-ê*-ýìíéý9ýõìííýNýRKPô Æçéíýõ8+ôý0$,1ý81,7 Íêì HUDPLFý&ìçíåý-%ýì+ýìíë.ð7ð$ Íëëðêäíçðíçí Íêë Íäé HUDPLFý+0çí6-ý&+ýíêíýèíí9ý Õéäíðèìëý0+ô Ìèì 5HIý1Rï Êëç Íëëðêäíçðäèë 4éì 7UDQVLVWRUý7&êçê.ý7ìéæ 5íæé 5ìçå 5HVý5-ê*-ýìíéý9ýõìííýNýRKPô 5217ý81,7 Õ9+ý$1ý8+ý02/6ô =HQHUý0$åíèìð0ýõ7ô Æçìíýõ9+ôý&+$66,6ý3$576 Front Unit VHF 7610 Exploded ViewUHF 7640 Exploded View Front Unit Schematic Diagrams and Component LayoutsVHF 7610 Block Diagram Main UnitVHF 7610 Transistor Basing Diagrams Foldout → VHF 7610 Main Board TOP View VHF Main Unit VHF 7610 Main Board SchematicUHF 7640 Block Diagram UHF 7640 Main Board Bottom View J4 T o O p tion al Un it UHF 7640 Main Board TOP ViewUHF 7640 Main Board Schematic VHF/UHF Front Unit Board Bottom View VHF/UHF Front Unit Board TOP ViewVHF/UHF Front Unit Schematic UHF 7640 Transistor Basing Diagrams