Harris Gates Five 994 9204 002 - Page 42

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Figure 5-2. PDM Loop

5-4 888-2314-001 Rev. T: Jan. 1996

WARNING: Disconnect primary power prior to servicing.

Main Page

Table of Contents10
Introduction13
Introduction17
- Three Phase Delta Distribution Transformers18
- Printed19
RF Output Connection20
Airflow Sensor Status21
Modulation Monitor Carrier Level22
Application of Audio23
- VSWR Detector26
- Introduction29
- PDM Amplifier30
High Voltage Supply Adjustment32
IPA Tuning33
- Overload Adjustment Procedures34
- Contactor Control35
- Power Output36
- VSWR Trips with High Levels of Modulation and High Power37
Symptom: Remote Control Functions Do Not Work37
- Possible Causes37
Troubleshooting am Noise38
- 50/60 Hz38
- Audio Lines Are Normally Balanced38
- 60 Khz38
- RFI Noise on Audio38
  - Transmitter Overall39
Introduction39
Personnel Protection39
Principles of Operation39
- FET'S in the GATES Series39
- PDM Theory in Brief39
- Polyphase Theory39
- Audio/Pdm Signal Flow39
- PDM Loop41
- RF Power Flow41
- Failsafe41
- AC Power Flow41
- High Voltage Power Supply41
Introduction45
- Section a63
- Oscillator (A16)63
Principles of Operation63
Replacement/Alignment63
Troubleshooting the RF Oscillator63
- Symptom: no Output63
Handling Mosfet's67
IPA Tuning and Testing67
- Procedure67
  - IPA Tuning67
- Ohmmeter Testing the IPA67
Principles of Operation67
- IPA Tuning Network67
Replacement/Alignment67
Testing Mosfet's68
- Section C71
- POWER AMPLIFIER A1 through A471
PA Toroids71
Principles of Operation71
Replacing a PA Module71
Troubleshooting the PA Boards71
- Ohmmeter Testing71
Handling Mosfet's72
RF Drive Phasing Measurement72
- Section D77
- Output Network77
Scoping the RF Drive72
Testing Mosfet's72
- Replacing PA Transistors72
Adjustment Procedures77
- Tuning and Loading Controls77
- Output Network Cold Tuning77
Principles of Operation77
Principles of Operation79
Replacement/Alignment79
Troubleshooting79
- Symptom: Detector Null Reading Is High and Cannot be Adjusted to Zero79
  - Bad Load Impedance79
  - Sample Signal Missing79
    - Section F83
    - Pdm Generator (A15)83
Principles of Operation83
Replacement/Alignment83
Troubleshooting PDM Generator83
- Symptom: no Pulses at J4, Causing Zero Power Out- Put from the Transmitter83
- Symptom: Imbalance in Output Pulse Widths84
  - Audio Imbalance84
  - Triangle Wave Imbalance84
- Symptom: Only One Output High85
- Symptom: Two Outputs Are High85
- Symptom: All Four Outputs Are High85
  - Section G89
  - Pdm Amplifier/Pull-Up (A6-A9)89
Maintenance89
- PDM Amplifiers89
- Gate Drive Checks89
- In-Circuit Ohmmetering the PDM Amp Module90
  - Checking Gate Drive92
Principles of Operation89
- PDM Amplifier89
- PDM Pull-Up Board89
Handling Mosfet's92
Testing Mosfet's92
- Section H95
- PDM FILTER (A10 and A11)95
Principles of Operation95
- Section J97
- Controller Board (A12)97
Principles of Operation97
- Coarse Power Level Control97
- Contactor Control97
- Fine Power Control97
- Metering97
- Overload Circuitry97
- Other Fault Detection98
- Controller Supply Voltages98
Replacement/Alignment Procedures98
- PA Voltage Electrical Zero98
- PA Volt Meter Calibration98
- Power Supply Current Calibration98
- Power Output Calibration99
Overload Adjustment Procedures99
- Power Supply Current Overload99
- Underdrive Fault99
- VSWR Detector99
Troubleshooting the Controller99
- Symptom: will Not Respond to an on Command99
  - Controller Supply Failure99
  - Failed Flip Flop Circuitry99
- Symptom: PDM Power Level Signal Cannot be con99
  - Section K103
  - Interface Board (A24)103
Principles of Operation103
Replacement/Alignment103
Troubleshooting103
- Symptom: Green Power Level Status Led's Light on Controller, but the Contactors Do Not Energize103
Introduction107

Harris Gates Five 994 9204 002 - Page 42

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