PossibleCauses................................6-14
ColorStat™ panel DC Regulator B+ and B- Supply
Faults.........................................6-14
ColorStat™panelOutputMonitorFaults.............6-14
+5Vand-5VSupplyFaults......................6-14
VSWRFaults .................................6-14
Symptom: Loss Of Positive Peak Capability...........6-16
PossibleCauses................................6-16
Symptom:HigherThanNormalAudioDistortion......6-16
PossibleCauses................................6-16
Symptom:ConsistentLossofRFAmplifiers..........6-17
Repeated Loss of Same RF Amplifier In Any Position 6-17
Consistent Loss Of An RF Amplifier In One Particu-
lar Position ...................................6-17
Consistent Loss Of Modules In Random Positions ....6-17
Other Troubleshooting Techniques ..................6-18
HandlingMOSFET’s...........................6-18
TestingMOSFET’s.............................6-18
FindingAMissingStep.........................6-18
Using FlexPatch™ for Bypassing a Failed PA Mod-
ule..........................................6-18
Using FlexPatch™ for Isolating Modulation En-
coder/RFAmplifierProblems....................6-19
MeasuringDriveLevel..........................6-19
MeasuringDrivePhasing........................6-19
RFAmplifierDrainPhasing......................6-20
Section VII
Parts List
Section VIII
Diagrams
Introduction......................................8-1
Section A
Oscillator (A17)
Introduction..................................... A-1
Location........................................ A-1
PrinciplesofOperation............................ A-1
CircuitDescription............................... A-1
Supply Voltages and Voltage Regulators ........... A-1
OscillatorStage................................ A-1
Buffer/SquaringAmplifier....................... A-1
FrequencyDivider.............................. A-1
ExternalInput................................. A-1
Normal or Combined Transmitter Operation......... A-1
FrequencyMonitorOutput....................... A-1
OscillatorSync................................ A-1
OscillatorOutput(Buffer-Driver).................. A-2
“RFPresent”Output............................ A-2
Troubleshooting ................................. A-2
Symptom: Oscillator LED on ColorStat™ panel is
Red,transmitterwillnotoperate.................. A-2
Symptom: No RF Output, External Oscillator Used . . . A-3
Symptom:FrequencyInstability................... A-3
Symptom:OutputAtIncorrectFrequency........... A-3
Symptom: Oscillator LED on ColorStat™ panel is
Redbuttransmitteroperationisnormal............. A-3
Section B
Buffer Amplifier (A16)
Introduction..................................... B-1
PrinciplesofOperation.......................... B-1
CircuitDescription................................ B-1
BufferAmplifierSupplyVoltage.................. B-1
FirstRFAmplifierStage(U1) .................... B-1
SecondRFAmplifierStage(Q1andQ2)............ B-1
ThirdRFAmplifierStage(Q3andQ4)............. B-1
Output Coupling Network........................ B-1
BufferAmplifierRFSense....................... B-1
Predriver Supply ............................... B-1
Troubleshooting.................................. B-1
Symptom: Buffer Amplifier LED on ColorStat™
panel is Red, transmitter will not operate............ B-1
Symptom: Buffer Amplifier LED on ColorStat™
panel is Red, transmitter will operate. .............. B-2
Section C
RF Amplifier
Introduction ..................................... C-1
PrinciplesofOperation............................ C-1
RFAmplifier:BasicTheoryOfOperation........... C-1
RFAmplifier:HalfQuadConfiguration............. C-1
RFAmplifier:FullQuadConfiguration............. C-1
RF Amplifier Module On/Off Control Circuit ........ C-1
RFTransformerPrimaryCurrent:AmplifierOff...... C-3
OscillatorSyncSignal........................... C-3
CircuitDescription................................ C-3
SupplyVoltage ................................ C-3
LEDIndicators................................. C-4
CableInterlock................................. C-4
RFDrive...................................... C-4
ControlSection ................................ C-4
RFOutput..................................... C-5
Troubleshooting.................................. C-5
Symptom:BlownFuseIndicatorIlluminated......... C-5
Section D
Driver Combiner/Motherboard (A14)
Introduction ..................................... D-1
CircuitDescription................................ D-1
BufferAmplifierConnections..................... D-1
Predriver...................................... D-1
DriverStage................................... D-1
ControlSignals................................. D-1
RFDriveCombiner............................. D-1
DriverTuning.................................. D-1
Section E
Driver Supply Regulator (A22)
Introduction ..................................... E-1
Location........................................ E-1
PrinciplesofOperation............................ E-1
CircuitDescription................................ E-1
+15VoltRegulator ............................. E-1
Control+VDCReference........................ E-1
PowerMOSFETOperation(AShortReview)........ E-1
RegulatorSectionCircuitDescription .............. E-2
DCAmplifierStage(Q2) ........................ E-2
Series Pass Transistors Q3, Q4, and Q7 (For Section
D8A Supply Voltage)........................... E-2
Series Pass Transistors Q5, Q6, and Q8 (For Section
D8BSupplyVoltage)........................... E-2
vi 888-2297-002 8/9/2000
WARNING: Disconnect primary power prior to servicing.
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