HP TM 11-6625-2779-14&P manual Defective Function, Carrier, Troubleshooting Input Amplifier

Page 48

Section V

Table 5-7. Function Troubleshooting

DEFECTIVE

 

 

FUNCTION

VF/Nm

CARRIER

 

 

 

75 UNBAL

 

A3K2

135 BAL

 

A1T2, A3K3,

 

 

A3R22,A3R23,

 

 

A3L1, A3R24

600 BAL

 

A1T2

600 BAL

A1T1

 

900 BAL

A1T1, A3K1,

 

 

A3R19, A3R20

 

NG

A1R5 thru

 

 

A1R8, A1C1,

 

 

A1S3

 

HOLD

L1A/B, A1S1

 

 

S1

 

DIAL BAT

A1S2, A3R59

 

a.First determine from the Front Panel Trouble Analysis chart (Table 5-9)exactly which range or ranges are defective.

b.Refer to Table 5-9to determine the changes that take place when switching ranges. Select the attenuator pads and/or gain switching resistors that match your symptom and check them.

5-36. TROUBLESHOOTING

THE

INPUT

AMPLIFIER.

 

 

a.Check the dc voltages as indicated in Figure 7-3to determine if a catastrophic failure does exist. If the dc voltages are abnormal (greater than + 10% of the indicated level), check for open or shorted components in the area of the abnormal indication.

b.Check to see that A3K1, A3K2 and A3K3 are operating properly. All relays are de- energized when either of the 600 BAL FUNCTION pushbuttons is depressed. Depress each of the other impedance functions (900 BAL, 135 BAL and 75 UNBAL) to see that A3K1, A3K3 and A3K2 respectively, energize and de-energize properly. If any relay fails to operate

Model 3555B

properly, check the relay and the energizing ground supplied through either pins 1, 2 or 3 on XA1.

5-37. FILTER TROUBLESHOOTING.

a.First determine that the set is operating in the TMS input mode. This bypasses the filters. If the set functions properly in the TMS mode, check each of the filters by applying a 1kHz signal at a 0dBm level to the set. All filters are calibrated for 0dBm indication on the 3555B meter at a frequency of 1kHz.

b.Since all the amplifiers in Figure 7-1are used in C MSG, the loss of any one will obviously cause the loss of the C MSG weighting. However, the bad amplifier can be isolated by checking the other filters. Use the following guide to isolate the trouble to a particular amplifier.

1.First be sure that the filters have the correct operating potential applied. Check the voltage at the junction of A4R49 and A4C33 to be sure that there is -20 volts + 1 volt.

2.If none of the filters work, check A3 in Figure 7-1(A4Q 11 through A4Q14).

3.If the PROG filter does not work but the others do, check A6 (A4Q5 and A4Q6).

4.If C MSG does not work but the others do, check A1, A4 and A5.

c.After the trouble has been isolated to an amplifier, check the dc potentials indicated

on the schematic diagram. This will normally isolate the trouble to a component. If the dc levels are correct but the filter response is out of tolerance, no attempt should be made to change the filter characteristics. Return the filter to your nearest -hp- Sales and Service office listed in the back of this manual.

5-38. TROUBLESHOOTING THE METER AMPLIFIER AND DETECTOR.

a.Inject a 1kHz, 0dBm signal (.775V rms) into the 3555B and set the INPUT switch to TMS TERM, RANGE to 0dBm and the FUNCTION to VF/Nm, 600 BAL. Measure the signal at the input of the meter amplifier (XA3 pin 9). The signal level

should be 6.2mV rms. If not the malfunction is ahead of the meter amplifier (refer to troubleshooting tree, Figure 5-8).

5-14

Page 47 Page 49
Image 48
Page 47 Page 49
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 List of Illustrations List of TablesIii Maintenance Forms, Records, and Reports Section IntroductionScope Administrative Storage Destruction of Army Electronics MaterielReporting Equipment Improvement Recommendations EIR 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 Filter Response Checks Filter Response ChecksMSG dBm 3kHz Flat dBm 15kHz Flat dBm Program dBm Input Balance Bridging LossTMS Brdg Input TMS BrdgAdjustment and Calibration Procedure Power Supply CheckUnbal Calibration Attenuator CalibrationFrequency Response Adjustment Common Mode AdjustmentBalance Check Assembly Removal Troubleshooting ProceduresFilter Calibration 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 Term11. Factory Selected Values 10. Resistance ChecksRange dBm Pin 1 to Pin 2 to 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 NumberAppendix C Manual Backdating ChangesTransmission and Noise Measuring SET 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
Top Page Image Contents