Harris DX 25U - Page 6

MeteringCircuits............................... E-3
Troubleshooting The Driver Supply Regulator.......... E-3
Symptom: Driver Sect D8A +VDC and Sect D8B
+VDCBothHigh.............................. E-4
Symptom: One Output Voltage Is +100 To +110
Volts,OtherCanBeAdjusted..................... E-4
Symptom: Both Driver Supply Regulator Output
VoltagesAreZero.............................. E-4
Symptom: One Driver Supply Output Voltage is
Zero,theOtherCanBeAdjusted.................. E-4
Symptom: Section D8B Voltage Increases Before
SectionD8AVoltageReaches+100Volts........... E-4
Symptom: Open Loop Operation is Correct, Closed
LoopOperationisFaulty......................... E-4
Section F
RF Multimeter (A23)
Introduction ..................................... F-1
CircuitDescription................................ F-1
MeteringDriverSectionParameters................ F-1
MultimeterProbe............................... F-1
Section G
RF Combiners:
Binary Combiner/Motherboard (A1)
and Main Combiner/Motherboards (A2 through A4)
Introduction .....................................G-1
PrinciplesofOperation ..........................G-1
CircuitDescription................................G-1
MainCombiner/Motherboards(A2throughA4)......G-1
BinaryCombiner/Motherboard(A1)................G-1
Section H
Output Sample Board (A26) and
Output Monitor (A27)
Introduction .....................................H-1
CircuitDescription................................H-1
OutputSampleBoard............................H-1
OutputMonitor.................................H-1
Section J
Analog Input Board (A35)
Introduction ..................................... J-1
CircuitDescription................................ J-1
Audio Input.................................... J-1
BesselFilter................................... J-1
InstrumentationAmplifier(U6,U9)................ J-1
BufferAmplifier(U7)........................... J-1
MaximumPowerAdjust(U7,R27) ................ J-1
AnalogDivider(U10) ........................... J-2
DigitallyControlledPotentiometer(U8)............. J-2
AnalogBuffer(U4)............................. J-2
DifferentialAmplifier/InverterU4.................. J-3
-(Audio+DC)SampleToDCRegulator............ J-3
AnalogInputBoardPowerSupplies................ J-3
BCD(BinaryCodedDecimal)Coding................ J-4
Troubleshooting .................................. J-4
Symptom: Normal Signal At TP4, No Signal At TP7
(DigitallyControlledPotentiometerOutput). ........ J-4
Symptom: Power Increases or Decreases in Steps,
NotContinuously.............................. J-4
Symptom:+15VDCor-15VDCfaults............. J-4
Section K
Analog To Digital Converter (A34)
Introduction..................................... K-1
PrinciplesofOperation............................ K-1
CircuitDescription............................... K-1
Converting a PA Sample to the A/D ENCODE Pulse
(T1,U29,Q9) ................................ K-1
FrequencyDivider(U29,Q9).................... K-1
ENCODESignalPulseWidth(Q9)................ K-1
Analog to Digital Converter Circuit................ K-1
ErrorDetectingCircuits......................... K-2
One-ShotOperation(U13,U14) .................. K-2
Big-StepSyncCircuit........................... K-3
ReconstructedAudioCircuit ..................... K-3
Maintenance.................................... K-4
PrintedCircuitboardMaintenance................. K-4
Adjustments................................... K-4
Troubleshooting ................................. K-4
Symptom: ColorStat™ panel CONVERSION ER-
ROR Indicator is RED, transmitter operates nor-
mally........................................ K-4
Symptom: ColorStat™ panel CONVERSION ER-
ROR indicator is RED, transmitter can be turned
ON.NoRFout................................ K-4
TechnicalAssistance.............................. K-5
ReplaceablePartsService.......................... K-5
Section L
Modulation Encoder (A37)
Introduction......................................L-1
PrinciplesOfOperation............................L-1
Modulation Encoding: Explanation and Example......L-1
CircuitDescription................................L-1
SupplyVoltages................................L-1
DigitalAudioDataCircuits.......................L-2
Inverter/DriverCircuits...........................L-2
CableInterlockCircuit...........................L-2
PAOffCircuit..................................L-3
BlownFuseCircuits.............................L-3
ClipCircuit....................................L-4
FlexPatch™......................................L-4
Example.......................................L-4
SingleRFAmpMomentaryTest...................L-4
Troubleshooting ..................................L-5
Symptom:SuspectedFaultyModulationEncoding ....L-5
Symptom:Red“PAOff”IndicatorIlluminated .......L-5
Symptom:CableInterlockIndication ...............L-5
SECTION M
DC REGULATOR (A30)
Introduction..................................... M-1
PrinciplesOfOperation........................... M-1
Circuit Grounds on the DC Regulator .............. M-1
UC3834IntegratedCircuitLinearRegulator......... M-1
B+ (+5.75 VDC) Regulated Supplies (DC Regulator) . M-2
Modulated B- Supplies.......................... M-3
Modulated B- Supplies: Circuit Description ......... M-3
Other Negative Regulated Supplies in the Transmitter. M-3
RegulatorOutputInhibitCircuit(U2).............. M-3
+5VDCSupply ............................... M-4
-5VDCSupply................................ M-4
8/9/2000 888-2297-002 vii
WARNING: Disconnect primary power prior to servicing.