HP TM 11-6625-2779-14&P manual Filter Calibration, Assembly Removal, Troubleshooting Procedures

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Section V

CARRIER function, change C4. To change the balance on VF/Nm, change the value of A1C9.

c.To determine whether the value of these capacitors should be increased or decreased, lightly touch the tip and ring banana jack insulators and watch the direction in which the meter indication goes. The side (tip or ring) that causes the meter indication to decrease needs added capacitance. The capacitance should be changed in very small steps and checked again.

5-24. FILTER CALIBRATION.

a.Connect the equipment as shown in Figure 5-5with S1 in position 1 and set the 3555B controls as follows:

FUNCTION ................VF/Nm, 600 BAL RANGE ....................................... 0dBm INPUT........................... NOISE, TERM NOISE WTG .......................3kHz FLAT

b.Connect a frequency counter to the 3555B AC MON terminals and adjust the 654A frequency to exactly 1.00kHz as indicated on the frequency counter. Adjust the 654A output level for exactly 0dBm.

c.Adjust A4R3C for 0dBm indication on the 3555B meter.

d.Change the NOISE WTG switch to 15kHz FLAT and note the meter indication. If it differs from the indication set up in step c, adjust A4R3C to split the difference between these two indications.

e.Change the 3555B NOISE WTG switch to C MSG and adjust A4R3A for 0dBm indication on the 3555B meter.

f.Change the 654A frequency to 3.00kHz and adjust A4R3D for an indication of - 2.15dBm on the 3555B meter.

g.Repeat steps e and f until both points are within specifications.

h.Change the 3555B NOISE WTG switch to PROG and change the 654A frequency back to 1.001Hz with the output level still set to 0dBm. Adjust A4R3B for 0dBm indication on the 3555B meter.

5-25. ASSEMBLY REMOVAL.

5-26. To gain access to the various assemblies in the 3555B use the following procedure.

a.Turn the set off and. remove it from the case by removing four front panel screws.

b.Unplug the small cable on the A3 assembly.

Model 3555B

c.Remove the two screws that secure the A3 board.

d.Gently lift up the bottom of the A3 board to unplug it from the A1 FUNCTION assembly.

e.Hold the bottom of the A3 board high enough to clear the FUNCTION board and pull the A3 assembly out. This is easily accomplished by gently rocking the board back and forth while pulling it down (toward the FUNCTION board).

f.Once the A3 assembly has been removed, the AI FUNCTION board can be removed by pulling it out.

g.To gain access to the RANGE attenuator (A2), Input switch and the NOISE WTG switch, the shield must be removed. To do this, remove the two screws on each side of the set and lift out the shield.

h.To reassembly the set, use the reverse of the procedure described above.

5-27. TROUBLESHOOTING PROCEDURES.

5-28. The following information is supplied to assist in locating a malfunction in the set in a minimum of time. It should first be determined that a malfunction does indeed exist and that the trouble is not external to the set.

5-29. Before starting to troubleshoot the set, use the front panel controls to determine exactly which function, if any, is operating properly. Table 5-6can aid you in this analysis. In many cases a good front panel analysis of the symptoms can lead you directly to the trouble.

5-30. To simplify troubleshooting the following information is supplied:

a. Troubleshooting Tree - - The troubleshooting tree (Figure 5-8)is based on the half-split method of troubleshooting a set. The trouble can be isolated to a general area or block using this tree. Once the trouble has been isolated to an area, a reference is given. to a paragraph where more specific information can be found.

b.Functional Block Diagram - - The functional block diagram can also be used to isolate the trouble to block. The diagram contains all of the essential blocks that make up the set and includes voltage levels, test points and adjustments. The troubleshooting tree and functional block diagram are keyed together by the numbers with a circle around them. If the levels or indications in your set do not agree with those on the functional block diagram or troubleshooting tree, refer to the paragraph indicated for more detailed information.

5-10

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Contents HEADQUARTERS, Department of the Army Reporting Errors and Recommending Improvements TM 11-6625-2779-14&PTechnical Manual Headquarters Department of the Army NSNReplaceable Parts Iii List of IllustrationsList of Tables Scope Maintenance Forms, Records, and ReportsSection Introduction Reporting Equipment Improvement Recommendations EIR Administrative StorageDestruction of Army Electronics Materiel Items Comprising an Operable Equipment Specifications Voice Frequency Level Measurements 20Hz to 20kHzSection Section General Information IntroductionAccessory Equipment Supplied Accessory Equipment SuppliedInstrument Identification BAL ModificationSection Installation Inspection Warranty ExceptionPower Requirements BatteryInstallation and Removal of Battery Cover RemovalControls Connectors Indicators BatterySection Operating InstructionsFront Panel Controls, Indicators, and Connectors Front, Side and Rear Pane Side Panel Controls and Connectors Level and Noise Measurements Level MeasurementsPage Noise Measurement Recorder Compatibility ApplicationsRecorder Compatibility Chart Identifying Noise Characteristics Transmission Loss MeasurementsCrosstalk Measurements Crosstalk Correction FactorMeasurements in DBC Reinstall the set in its case 0dBmInput jacks are connected in parallel. If a 600 ohm 135 BALStep Procedure Level Measurement Noise Metallic MeasurementsNoise-to-Ground Measurements Balance Measurement Recorder CalibrationExample Transmission Loss MeasurementBlock Diagram Description Section Theory of Operation IntroductionDetailed Circuit Description Simplified Dial BAT FunctionInput Amplifier A3. Schematic No Range Attenuator A2Setting Attenuation FILTERS. Schematic NoRange Attenuator Pads UsedKHz Flat and Program Weighting Curves C-MSG and 1SkHz Flat Weighting Curves Meter AMPLIFIER. Schematic No DETECTOR. Schematic NoPower Supply and Series Regulator Schematic No Section Maintenance Introouction Instrument Recommended Type Required Characteristics ModelFactory Selected Values BAL ConversionPerformance Checks Level Accuracy ChecksFunction CARRIER, 75 Unbal TMS, TermUnbal Carrier Accuracy Check RangeFrequency 30Hz to 1MHz 100Hz to 600kHz 1MHz to 3MHzReturn Loss Check 20Hz to 20kHz 40Hz to 15kHz 100Hz to 20kHz 100Hz to 15kHzReturn Loss Test Set-Up MSG dBm 3kHz Flat dBm 15kHz Flat dBm Program dBm Filter Response ChecksFilter Response Checks Input Balance Bridging LossTMS Brdg Input TMS BrdgAdjustment and Calibration Procedure Power Supply CheckUnbal Calibration Attenuator CalibrationBalance Check Frequency Response AdjustmentCommon Mode Adjustment Filter Calibration Assembly RemovalTroubleshooting Procedures Troubleshooting Tree Front Panel Trouble Analysis Dial BATFront Panel Troubleshooting Function TroubleshootingRange Troubleshooting Front Panel Trouble Analysis ContdTroubleshooting Input Amplifier Filter TroubleshootingTroubleshooting the Meter Amplifier and Detector Defective FunctionFunction Switch Resistance Values Function Input Jacks DIAL/AC MON JacksTip to Ring Tip to Ground Ring to Ground Brdg TermRange dBm Pin 1 to Pin 2 to 11. Factory Selected Values10. Resistance Checks Performance Check Test Card Description CheckCarrier 75 Unbal Level Accuracy Check Carrier 135 BAL Level Accuracy CheckPerformance Check Test Card Contd Carrier 600 BAL Level Accuracy CheckReturn Loss Check Filter Response Checks MSGProgram Bridging Loss CheckSection Replaceable Parts Introduction Ordering InformationReplaceable Parts 03555-66507 PC Board Assy functionReplaceable Parts Contd 03555-66508 Board Assy amplifierA3 Contd 03555-66506 PC Board Assy filter A4 Contd Chassis Mounted Components Chassis Mounted Components Contd MiscellaneousMiscellaneous Contd Replacement National Part Stock Number Fscm Part Number National Stock Number Cross Reference IndexFscm National Stock NumberPage Model 3555B Appendix a Code List of Manufacturers Circuit Diagrams Functional Block DiagramSchematic Diagrams Reference DesignationsSection Model 3555B Functional Block Diagram 7-4A1 Function Assembly Schematic and Component Location 7-67-8 A4 Filter Schematic and Component Location 7-1011/7-12 Appendix a ReferencesMaintenance Allocation Section I. Introduction General Maintenance FunctionAppendix B Column EntriesTool and Test Equipment Requiremen ts Sec Remarks SecAudio Level Meter TA-885/U TM 11-7725-2779-14&P REF Code NumberTransmission and Noise Measuring SET Appendix CManual Backdating Changes Delete CR6 across M1 Government Printing Office 1980-603-128/66General, United States Army Chief of StaffMajor General, United States Army Adjutant General Active ArmyPage PIN
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