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Harris DX 25U Technical Manual

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TECHNICAL MANUAL
DX 25U MEDIUM WAVE TRANSMITTER
T.M. No. 888-2297-002
© Copyright HARRIS CORPORATION
1994, 1995, 1996, 1997, 1998, 1999, 2000 All rights reserved
994 9168 001
I
Introduction/Specifications
II
Installation
III
Operation
IV
Theory
V
Maintenance
VI
Troubleshooting
VII
Parts List
Subsections
VIII RF
Oscillator
Buffer Amplifier
RF Amplifier Modules
Driver Combiner/Motherboard
Driver Supply Regulator
RF Multimeter
RF Combiners
Output Sample Board &
Output Monitor
IX
Audio
Analog Input Board
Analog to Digital Converter
Modulation Encoders
DC Regulator
External Interface
X
Control
Controller
LED Board
Switch Board/Meter Panel
Driver Encoder/Temp Sense Board
Printed: August, 2000
Rev. AA: 8-9-2000

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  • Page 1 Introduction/Specifications TECHNICAL MANUAL Installation Operation Theory DX 25U MEDIUM WAVE TRANSMITTER Maintenance Troubleshooting 994 9168 001 Parts List Subsections VIII RF Oscillator Buffer Amplifier RF Amplifier Modules Driver Combiner/Motherboard Driver Supply Regulator RF Multimeter RF Combiners Output Sample Board &...
  • Page 2  ...

  • Page 3: Table Of Contents

    TABLE OF CONTENTS Section I Control Inputs ....... . 2-13 Introduction/Specifications Analog Monitoring Outputs .
  • Page 4 Spark Gap, E2 ....... . . 4-8 Symptom: Transmitter will not turn on - all Color- Digital Modulation Principles .
  • Page 5 Possible Causes ....... . 6-14 Principles of Operation ......B-1 ColorStat™...
  • Page 6 Metering Circuits ....... E-3 Section K Troubleshooting The Driver Supply Regulator..E-3 Analog To Digital Converter (A34) Symptom: Driver Sect D8A +VDC and Sect D8B Introduction .
  • Page 7 Fault Detection Circuits ......M-4 Up-Down Counters: Setting and Storing Digital B+ Fault Circuit ....... M-4 Power Data .
  • Page 8 Type 5 Faults ........Q-4 Maintenance ........R-2 Type 6 Faults .
  • Page 9 MANUAL REVISION HISTORY 994 9168 001 888-2297-XXX Rev. Date Pages Affected 002-A 09-23-94 39409 Title Page and pages 7-7 to 7-9. Added MRH-1/MRH-2 002-A1 12-12-94 Errata Misc pages - reference to 839 7855 068 & 839 7855 122 changed to 839 7855 151 002-B 01-09-95 39470 Title Page, MRH-1/MRH-2, and pages 7-4 to 7-7...

  • Page 11: Section I

    Section C, RF Amplifier Modules (A101-A244) NOTE • Section D, Driver Combiner/Motherboard (A14) • Harris maintains a policy of continuous improvements on its Section E, Driver Supply Regulator (A22) equipment and therefore reserves the right to change specifica- • Section F, RF Multimeter (A23) tions without notice.
  • Page 12 DX-25U Figure 1-1. DX 25U Front View with Doors Closed Figure 1-2. DX 25U Rear View with Doors Closed 888-2297-002 Rev. R: 11-11-96 WARNING: Disconnect primary power prior to servicing.

  • Page 13: Installation/Initial Turn On

    This section provides information and instructions necessary for technical manuals for the transmitter and other equipment the installation and initial turn on of the HARRIS DX-25U to see if specialized tools are required. Make arrangements MEDIUM WAVE TRANSMITTER, including AM Stereo In- to obtain them if necessary.

  • Page 14: Factory Test Data

    It includes HARRIS part number 099 0002 238 meter readings, measured performance data, frequency determined Paste flux (Engelhard Ultra-Flux 1 lb jar) HARRIS part parts and adjustments for your transmitter. number 099 0002 241...

  • Page 15: Cabinet Bolts

    Section II - Installation Compartment end of the cabinet and should be fork lifted from Air System And Cooling this end. If roller bars are used, lead with the heavier end. Refer to Sheet 2 of the DX-25U Cabinet Outline Drawing, 839-7855-152, for information on air flow CFM, heat dissipation CAUTION and duct work dimensions.

  • Page 16: Interconnection Wiring

    DX-25U Transformer Tap Settings 2.8.4 Tapping information for T1 and the blowers will be found on Table 2-2, wire and fusing information will be found on Sheet 3 of the DX-25U Cabinet Outline drawing, 839-7855-152. Tap- ping information for Low Voltage Supply transformer T2 is silk screened on the center door and labeled on the transformer.

  • Page 17: Rf Output Connection

    Section II - Installation CAUTION sufficient for the type of testing to be done. The peak power should be considered when selecting a water cooled load. THE TRANSMITTER MUST BE GROUNDED WITH A LOW IMPED- ANCE PATH. THE OUTER CONDUCTOR OF THE RF TRANSMIS- SION LINE IS NOT AN ADEQUATE GROUND.

  • Page 18: Modulation Monitor Connection

    DX-25U • Frequency Monitor Connection. 2.12.3 TB3-3: Audio (-) • TB3-4: Optional shield connection, capacitively coupled to If a frequency monitor is used at the transmitter site, a coaxial transmitter chassis ground. cable should be run from BNC jack J5 on the Oscillator to the Audio Input TB3 is shown on sheet 2 of the DX-25U Overall frequency monitor input.

  • Page 19: Pre-Turn On Checks (Mechanical)

    Section II - Installation Pre-Turn On Checks (Mechanical) b. Underdrive overload test. 2.13 c. PA Power Supply check. Although appropriate packaging and shipping precautions are taken before the equipment leaves the factory, hardware some- d. Fan rotation check. times works loose during shipment. The transmitter should be e.

  • Page 20: Underdrive Overload Test

    DX-25U a. Single phase AC power ON, three phase AC power OFF. WARNING b. Depress the LOW power button. Observe the following: TURN OFF SINGLE PHASE AND THREE PHASE PRIMARY 1. K1 step start contactor should energize, quickly drop POWER AT THE MAIN DISCONNECT BEFORE REMOVING ANY out, energize, then drop out a second time.

  • Page 21: Driver Operation Check

    Section II - Installation a. Single phase ON, three phase ON, CB1 and CB2 ON, PA a. Remove the clip lead between TP8 and GND on the LED Off switch S2 OFF. Board if used in checking out the PA Power Supply. b.

  • Page 22: Setting Modulation Monitor Sample Levels

    DX-25U b. Replace all rear panels and apply single phase and three VDC, PA Supply Current should be between 110 and 115 Amps. phase AC power to the transmitter. The Low Voltage circuit breakers CB1 and CB2 should be ON and the PA OFF d.
  • Page 23 Section II - Installation Table 2-4. Minimum Recommended Control and Status Functions for Remote Control Rev. AA: 8/9/2000 888-2297-002 2-11 WARNING: Disconnect primary power prior to servicing.

  • Page 24: Modulation Check

    DX-25U j. Turn R8, HIGH power modulation monitor sample adjust- transmitter can accommodate reference levels from -10 dBm to +10 dBm at 600 Ohms.) ment, on Output Monitor fully CCW. b. Switch the transmitter to MEDIUM power. Set the output k.

  • Page 25: Recording Normal Meter Readings

    4 Volt input limit of remote control typically optimizes efficiency, IPM and mono THD and IMD. systems such as the Harris Sentinel. If the remote control system The bandpass tuning can be adjusted while the transmitter is ON input is not high impedance, the loading on the monitor output and modulating.
  • Page 26 DX-25U or can provide a logic LOW output when a pull-up resistor to +5 e. RAISE/LOWER inputs change the RF power. A RAISE to +15 VDC is used. Maximum safe voltage at a status output input will cause transmitter power output to INCREASE terminal is +15 VDC and maximum safe current into a status for as long as the control input is provided, or until the output is 100 mA.
  • Page 27 Section II - Installation Table 2-5. Initial Turn-On Meter Readings Rev. AA: 8/9/2000 888-2297-002 2-15 WARNING: Disconnect primary power prior to servicing.
  • Page 28  ...

  • Page 29: Operators Guide

    Section III Operators Guide Introduction If any indicators are still red after operating the RESET, do not attempt to turn on the transmitter and contact qualified This section contains information on day-to-day operation for maintenance personnel. the non-technical operator. Transmitter Turn-On Procedure Operating Procedures When the Preoperational Checkout has been completed and no These procedures describe normal daily operation of the DX-...

  • Page 30: Transmitter Operations

    DX-25U c. With the POWER switch in the FORWARD position, the required to turn the transmitter ON and to reset power levels on Power meter should indicate zero power. Supply voltage and the LOW, MEDIUM and HIGH positions. supply current meters should both indicate zero readings. 3.6.2.3 Power Supply Current Fault During a Current Fault condition the transmitter will shut off and the indicator will change to RED.
  • Page 31 Section III - Operation 3.6.2.8 RF Amp Fuse RESET. The fault must be corrected to clear the fault indication. The transmitter will continue to operate safely, although power Continue normal operation and contact qualified maintenance output will be slightly reduced. The fault indication can not be personnel.
  • Page 32  ...

  • Page 33: Section Iiia

    Section IIIA Controls and Indicators Figure 3A-1. DX 25 Front View, Controls and Indicators Table 3A-1. DX 25U Transmitter, Controls and Indicators REF. CONTROL/INDICATOR FUNCTION LOAD Control Control for matching load to 50 Ohm transmitter impedance. TUNE Control Control for matching load to 50 Ohm transmitter impedance.
  • Page 34 DX-25U Figure 3A-2. Switchboard/Meter Panel Controls and Indicators Table 3A-2. Switchboard/Meter Panel Controls and Indicators REF. CONTROL/INDICATOR FUNCTION VOLTAGE multimeter Indicates voltages at points selected by the Multimeter Switch (Ref. 11). SUPPLY CURRENT meter Indicates the 230V supply current being supplied to the Power Amplifier. POWER meter Indicates either FORWARD or REFLECTED power at the transmitter output, whichever is selected by the POWER METER selector switch (Ref.
  • Page 35 Section IIIA - Controls and Indicators Figure 3A-3. ColorStat™ Panel Controls & Indicators Table 3A-3. ColorStat™ Panel Controls & Indicators REF. CONTROL/INDICATOR FUNCTION LOCAL/REMOTE, switch Selects LOCAL or REMOTE control of the transmitter. (Remote monitoring is operational in either the LOCAL or REMOTE switch position.) LOCAL, status indicator Indicates that the remote control inputs to the transmitter are disabled, and only local con- trol is possible.
  • Page 36 DX-25U Table 3A-3. Status Panel, Controls and Indicators (Cont.) REF. CONTROL/INDICATOR FUNCTION 10 OUTPUT MONITOR, BAND- Bicolor LED indicator. GREEN indicates that there is low reflected power at the input of PASS FILTER VSWR indicator the bandpass filter; RED indicates that reflected power at the filter input is above the level set by the VSWR trip adjust control.
  • Page 37 Section IIIA - Controls and Indicators Table 3A-3. Status Panel, Controls and Indicators (Cont.) REF. CONTROL/INDICATOR FUNCTION 26 DC REGULATOR, B+ supply Bicolor LED indicator. Indicates status of +5 Volt supply on the DC Regulator board. status indicator GREEN indicates normal operation; RED indicates +5 Volt supply fault. 27 DC REGULATOR, B- supply Bicolor LED indicator.
  • Page 38 DX-25U Table 3A-5. Boards Listed in Numerical Order Table 3A-4. Boards Listed in Alphabetical Order A5 thru A7 Main Combiner Motherboard Analog Input Board Binary Combiner Motherboard A/D Converter Board Driver Combiner Motherboard Buffer Amplifier RF Drive Splitter Combiner Motherboard Binary Buffer Amplifier Combiner Motherboard Main A5 thru A7...
  • Page 39 Section IIIA - Controls and Indicators Figure 3A-4 Left Control Compartment - Front View 839 7855 117 Rev AA: 8/9/2000 888-2297-002 3A-7 WARNING: Disconnect primary power prior to servicing.
  • Page 40 DX-25U Figure 3A-5 Center Control Compartment - Front View 839 7855 118 3A-8 888-2297-002 Rev AA: 8/9/2000 WARNING: Disconnect primary power prior to servicing.
  • Page 41 Section IIIA - Controls and Indicators Figure 3A-6 Driver Compartment - Front View 839 7855 119 Rev AA: 8/9/2000 888-2297-002 3A-9 WARNING: Disconnect primary power prior to servicing.
  • Page 42 DX-25U Figure 3A-7 Driver Compartment - Rear View 839 7855 126 3A-10 888-2297-002 Rev AA: 8/9/2000 WARNING: Disconnect primary power prior to servicing.
  • Page 43 Section IIIA - Controls and Indicators Figure 3A-8 Left & Center Control Compartments - Rear View 839 7855 121-modified Rev AA: 8/9/2000 888-2297-002 3A-11 WARNING: Disconnect primary power prior to servicing.
  • Page 44 DX-25U Figure 3A-9 Output Network Compartment - Rear View 839 7855 120 3A-12 888-2297-002 Rev AA: 8/9/2000 WARNING: Disconnect primary power prior to servicing.
  • Page 45 Section IIIA - Controls and Indicators Figure 3A-10 Step Start Panel, Unit 3 839 7855 139 Rev AA: 8/9/2000 888-2297-002 3A-13 WARNING: Disconnect primary power prior to servicing.
  • Page 46  ...

  • Page 47: Overall System Theory

    Section IV Overall System Theory 4.2.1.5 Driver Supply Regulator Introduction The Driver Supply Regulator is part of a loop which controls RF This section presents the overall principles of operation for the drive level to the power amplifier. An “RF Sense” feedback signal DX-25U AM TRANSMITTER, including a review of Digital from the RF splitter controls the regulator output voltage to Modulation, and circuits not described in SECTIONS A through S.

  • Page 48: Controller Section

    DX-25U Controller Section The Bandpass Filter stage completes the digital to analog con- 4.2.3 version by filtering out the individual “step” voltages generated The Controller section consists of the Controller, LED Board, by the RF amplifiers. External Interface, and the Switch Board/Meter Panel. The Pi Network provides for impedance matching into antenna 4.2.3.1 Controller systems that are not perfect 50 Ohm loads.
  • Page 49 Section IV - Overall System Theory Figure 4-1. DX 25U Block Diagram Rev. AA: 8-9-00 888-2297-002 WARNING: Disconnect primary power prior to servicing.

  • Page 50: Power Distribution Board, A39

    DX-25U supplies the Buffer Amplifier. The winding also supplies 24 turn-on/turn-off logic. Approximately one-half second later, Volts AC for the interlock circuit relays. step-start contactor K1 de-energizes. The other secondary winding is tapped to provide two different PA Supply Discharge Circuit (Crowbar) 4.4.2 output voltages for bridge rectifiers, CR13 and CR14.

  • Page 51: Supply Current Meter, M2

    Section IV - Overall System Theory provides +60 VDC for the Predriver and Binary Amplifiers and Refer to SECTION J, Analog Input Board, for the circuit de- is filtered by 10 mH choke L3 and capacitors C10 and C42. scription. 4.4.12.2 Driver Supply Regulator Sample Supply Current Meter, M2 4.4.8...

  • Page 52: Fans

    DX-25U Fans External Interlock Circuit 4.5.1 4.6.2 Four fans, B1 through B4, are used in the DX-25U for transmit- The external interlock circuit turns the transmitter OFF if any ter cooling. Each fan uses a 1/3 HP, dual voltage 3-phase motor, external interlock interrupts the normally closed connection powered when T1 is energized.

  • Page 53: Power Amplifier Description

    Section IV - Overall System Theory on a PA Combiner/Motherboard. All RF drive cables are the SUMMARY: The more “steps” or RF amplifiers that are turned same length, so that all PA Module inputs are in phase. on, the more power will be transmitted. The DX-25U uses a combination of 58 equal RF voltage “Big Step”...

  • Page 54: Rf Samples From The Output Combiner

    DX-25U Refer to the following sections for additional information on the output power. The combiner output impedance is low, approxi- Power Amplifier: mately 8 Ohms, and is matched to approximately 50 Ohms. a. SECTION A: RF Amplifier Module. The bandpass filter also “smooths” the small steps in the output signal that remain after the Digital to Analog conversion by the b.

  • Page 55: Analog To Digital Conversion

    Section IV - Overall System Theory and 1/64 step. In this series, each step is divided by two bits, it may represent 2 =64 quantities. If a digital word to get the next step. A Binary series could also be 1, 2, 4, has 12 bits, it may represent 2 =4096 quantities.

  • Page 56: Amplitude Modulation In The Dx-25U

    DX-25U word represent the total number of “BIG STEP” RF amplifiers switched OFF. As the audio signal changes from instant to ON at any time. For example: instant, the number of RF amplifiers that are ON changes. a. 010111/XXXXXX = 23 BIG STEPS ON a.
  • Page 57 4.9.6.1 Digital Modulator Characteristics The patented Harris Digital Modulator uses new technology which produces a very high quality, low distortion amplitude modulated signal for AM broadcasters.
  • Page 58  ...

  • Page 59: Maintenance/Alignments

    Section V Maintenance/Alignments Introduction 1. Overheating, which is indicated by discoloration, bulg- ing of parts, and peculiar odors. This section provides general system preventive maintenance 2. Oxidation. information, board replacement and alignment procedures and a transmitter frequency change procedure. 3. Dirt, corrosion, rust, mildew, and fungus growth. •...
  • Page 60 DX-25U d. Use standard practices to repair poor solder connections e. Be sure to include an inspection of the power supply with a low-wattage soldering iron. discharge switches S9, S10 and S12 located in the inter- locked RF Amplifier and Driver Compartments. e.

  • Page 61: Module Replacement/Alignment

    Section V - Maintenance verify that they are near the measurements indicated on the Factory Test Data sheet. NOTE Adjustment of Predriver tuning control L1 is NOT required when replacing the module. Changing the Predriver tuning can affect the setting of the Oscillator sync used for VSWR protection. If the Predriver is replaced and a Predriver Fault is still indicated on the ColorStat™...

  • Page 62: Rf Drive Splitter Removal

    DX-25U The following test applies to all MOSFET’s used in the transmit- d. Reattach heatsinks in reverse order as they were removed. ter, but is not necessarily applicable to MOSFET’s used in other Tighten heatsink and pc board screws first and then tighten equipment.

  • Page 63: Controller A38

    Section V - Maintenance Controller A38 5.5.2 2. On the Driver/Combiner motherboard, the secondary rod will have to be removed through the top of the Once a new Controller is installed the low voltage circuit break- transmitter. If top removal is not possible because of an ers CB1 and CB2 can be turned on.

  • Page 64: Analog To Digital Converter (A34)

    DX-25U 5.6.1.2 Offset Adjustment: R7 These boards are: The Offset adjustment is set during factory testing of the board, • Analog to Digital Converter (A34) but can be adjusted if needed. The most significant affect of the • Analog Input Board (A35) offset adjustment is on modulation tracking.

  • Page 65: Oscillator (A17)

    Section V - Maintenance c. Depress the HIGH power button. If HIGH power was b. Use a scope to display one cycle of demodulated audio previously set for 25 kW, the transmitter output should now from the modulation monitor. be approximately 25 kW. c.

  • Page 66: Driver Supply Regulator (A22)

    DX-25U d. To set the output frequency of crystal Y2, turn off the low To remove the printed circuit board, the seal between the transis- voltage and move jumpers J1 and J6 to positions 1-3. tors and the insulator pads will have to be broken. Use a long Repeat the above procedure by adjusting C3.

  • Page 67: Output Monitor (A27)

    Section V - Maintenance c. Adjust the voltage of “REG B B- OUT” with R93 and that the vertical sensitivity of both channels of the scope “REG A B-OUT” with R51 for approximately 2.5 VDC are the same. with the Low Voltage ON. i.
  • Page 68 DX-25U e. Set the Normal/Calibrate switch S8 to the Normal position, c. Adjust R24 until the voltage matches the Factory Test Data and release momentary pushbutton switch S5. Make sure sheet. that the vertical sensitivity of both channels of the scope is If the Factory Test Data sheet is unavailable or if it is necessary the same.

  • Page 69: Led Board (A32)

    RF Amp Compartment access door. a. Turn off the Low Voltage supply at CB1 and CB2. f. Connect 10x scope probe with an extended tip, Harris part b. Remove all cables from the LED Board. 610-1131-000, through the door to the anode of CR3 in front of the heatsink.
  • Page 70 DX-25U i. To turn on an RF amplifier, depress the LOW power button note the voltage of D8A and D8B on the RF MULTIME- and note that the PA Power supply voltage comes up as TER. indicated on the front panel multimeter but no RF power b.

  • Page 71: Driver Encoder/Temp Sense Board (A19)

    Section V - Maintenance • c. Adjust the AVERAGE CURRENT overload R42 until the TP2 (R19): Driver Threshold ON • OVERCURRENT LED lights AMBER. TP3 (R49): Temp Cal • TP4 (R50): Step 1 Temp d. Modulate the transmitter with 100 Hz at 100%. •...

  • Page 72: Switch Board/Meter Panel (A31)

    DX-25U 5.6.8.3 Air Flow Monitor Circuits WARNING Set the Air Flow Monitor circuits on the Driver Encoder/Temp ENSURE ALL PRIMARY AC VOLTAGE HAS BEEN REMOVED Sense Board as follows: FROM TRANSMITTER AND A GROUNDING STICK IS USED TO NOTE GROUND ALL POINTS WHERE AC OR RF POWER HAS BEEN For all adjustments and verifications, allow the air sensor at APPLIED BEFORE PROCEEDING WITH THE FOLLOWING PRO- least one minute to stabilize.

  • Page 73: Frequency Change Procedure

    Section V - Maintenance Table 5-7. Frequency Determined Jumpers and Switches WARNING ENSURE ALL PRIMARY AC VOLTAGE HAS BEEN REMOVED FROM TRANSMITTER AND A GROUNDING STICK IS USED TO FREQUENCY GROUND ALL POINTS WHERE AC OR RF POWER HAS BEEN BOARD DETERMINED APPLIED BEFORE PROCEEDING WITH THE FOLLOWING PRO-...

  • Page 74: Rf Circuits Checkout

    DX-25U • c. Attach a 10x scope probe, Harris part #610-1131-000, Example: for a carrier frequency of 1000 kHz; A = 100,000/(1.257 x 1000) + 42 = 121.5 = 121.5 ∠90 or 0 + through the ventilation slots in the interlocked Driver j121.5.

  • Page 75: Initial Driver Tuning And Setup

    P1 on the Analog Input Board. n. Adjust R2 until the drive level reaches 24.0 Vp-p on the b. Connect the 10x scope probe, Harris part #610-1131-000, scope or the DRIVER D8A voltage reaches 100 Volts. to CR3 or CR4 on PA Module RF33 through the ventilation 1.

  • Page 76: Initial Tuning At Low Power

    DX-25U former T10 may need to be used to increase, or “BOOST”, 1. A25: F1-F8 the amplitude of the drive. This is achieved by attaching 2. A24: F1-F9 reversing the lead connections on the transformer winding 3. F20: (on top of T1) to the combiner bar and the combiner bar cover.

  • Page 77: Tuning At High Power

    See the adjustment procedures under the Analog Input Modulation) products. Board and DC Regulator replacement sections in this section. a. Connect the 10x probe, Harris part #610-1131-000, to the drain TP1 test point of Q3 on PA Module RF33 by inserting Tuning At High Power 5.7.8...

  • Page 78: Other Adjustments

    DX-25U k. Operate the transmitter again at 25 kW. If no waveform transition. You may also see that there is now a transition at Step 37 and Step 38 also. See Figures 5-11 and 5-12. appears, then depress the RAISE or LOWER button until this step turns on.
  • Page 79 Section V - Maintenance Figure 5-4 Figure 5-2 RF Drive Waveform at RF Amplifier, Gate of Q3 (anode of Predriver Input drive waveform, measured at the anode of CR3 CR3). RF AMplifier turned ON. (5Vp-p per division) or CR4 on Predriver module (2Vp-p per division) Figure 5-5 Figure 5-3 Antenna VSWR Detector voltage and current samples as meas-...
  • Page 80 DX-25U Figure 5-8 Figure 5-6 Modulated B- waveform at DC Regulator A30TP30. 25kW op- Demodulated Audio of 100 Hz sinewave at 30% modulation at eration with 100 Hz, 100% modulaltion. 25 kW. Scope view of positive peak expanded to show glitches due to improper A to D phasing adjustment.
  • Page 81 Section V - Maintenance Figure 5-10 Figure 5-12 Oscillator sync samples at Oscillator A17TP4 and TP5. Trans- Demodulated audio. Transmitter operaeting at 5kW with 100 mitter operating at 25 kW with no modulation. The two sam- Hz, approximately 10% triangle modulation. ples are in phase.
  • Page 82  ...

  • Page 83: Troubleshooting

    Section VI Troubleshooting Introduction This section contains techniques and guidelines to assist the engineer in isolating the problem more quickly. The engineer This section of the technical manual contains troubleshooting using this section of the manual must have the proper test procedures for the DX-25U.
  • Page 84 DX-25U Possible Causes ................6-8 Modulation not reaching transmitter .
  • Page 85 Section VI - Troubleshooting ColorStat™ panel Predriver Fault ............. . 6-13 ColorStat™...
  • Page 86 DX-25U Improper Overload Settings 6-17 Improper Air Flow 6-17 Transmitter Mistuning 6-17 Other Troubleshooting Techniques ............. 6-18 Handling MOSFET’s .
  • Page 87 Section VI - Troubleshooting Table 6-1. DX 25U Fault Types TYPE 1 TURNS PA POWER SUPPLY OFF (Manual Restart Required) External Interlock Air Flow Fault DOOR Door Interlock SUPPLY FAULT PA Power Supply Protection OVER VOLTAGE PA Power Supply Overvoltage Protection...

  • Page 88: Symptom: Transmitter Will Not Turn On - No Color-Stat™ Panel Indicators Are Illuminated

    DX-25U Symptom: Transmitter will not turn WARNING ON - No ColorStat™ panel indica- TO MEASURE THE VOLTAGES IN THE FOLLOWING STEP RE- tors are illuminated. MOVE PRIMARY VOLTAGE AT THE MAIN BREAKER OR FUSE PANEL. THEN REMOVE THE STEP START PANEL COVER AND Possible Causes 6.2.1 ATTACH YOUR MEASURING DEVICE TO THE TERMINALS...

  • Page 89: Possible Causes

    Section VI - Troubleshooting Symptom: Transmitter will not turn To check, remove the wire connected to the Customer Remote control terminal strip TB1-22. on - one or more ColorStat™ panel 6.6.1.2 Type 4 or Type 5 Fault indicators are illuminated RED. Regulator faults that occur on the Analog to Digital Converter and the Analog Input Board will generate a Type 4 fault and Possible Causes...

  • Page 90: Symptom: Unable To Raise Power Past A Certain Point. Colorstat™ Panel Ant And/Or Filter Led In- Dicate Red

    DX-25U c. No ColorStat™ panel indicators are illuminated RED. appropriate Encoder output. Refer to SECTION L, Modulation Check the Over Temp LED DS2 on the Driver En- Encoders, for additional information. coder/Temp Sense Board. If it is RED, the circuitry has 6.9.1.4 Open fuses on Fuse Boards A24 or A25.

  • Page 91: Faults With Tone Modulation. Possible Causes

    Section VI - Troubleshooting sub-audible signals without degrading the ON AIR sound in SECTION P, Controller, and SECTION J, Analog Input of the transmitter. Board, for additional information. c. DC OFFSET: Some audio processors have a DC offset which can shift with modulation, at either a sub-audible WARNING or audio rate.

  • Page 92: Colorstat™ Panel Supply Fault

    DX-25U the three phase line voltages are well balanced. If the balance is WARNING marginal, then Supply fault overloads could occur. ENSURE ALL POWER IS REMOVED FROM TRANSMITTER AND 6.13.1.5 Overload Settings THAT THE GROUNDING STICK HAS BEEN USED TO DIS- Refer to SECTION V, Maintenance, for the Power Supply CHARGE ANY RESIDUAL VOLTAGE WHERE POWER HAS Protection overload adjustment procedure.

  • Page 93: Colorstat™ Panel Overdrive Fault

    Section VI - Troubleshooting C10, L3. Refer to the DX-25U Overall Schematic in the Draw- the OPEN position, but it will not have the Automatic gain ing Package for circuit details. control feature enabled. 6.14.1.4 No Drive To The Driver Stage 6.14.1.9 Defective Driver Encoder Signals The Driver Modules require a minimum of 20Vp-p of drive to Check the PA Module control signals from the Driver En-...

  • Page 94: Colorstat™ Panel Door Interlock

    DX-25U malfunction. Refer to SECTION E, Driver Supply Regulator, ColorStat™ panel Air Interlock 6.18 for additional information. Air interlock problems will be either intermittent, as could occur if an air filter becomes blocked, or constant, as during a two or more fan failures.

  • Page 95: Colorstat™ Panel Buffer Fault

    Section VI - Troubleshooting output is not sufficient. Refer to SECTION A, Oscillator, for NOTE additional information. It is sometimes possible for the regulator circuit to lock into a fault condition if the output is accidentally shorted. If this oc- curs, turn off the Low Voltage at CB1 and CB2 for approxi- mately 1 minute to allow the power supply to discharge.
  • Page 96 DX-25U L, Modulation Encoder, for additional information and circuit ColorStat™ panel Output Monitor 6.27 description to help facilitate troubleshooting an interlock prob- Faults lem. +5V and -5V Supply Faults 6.27.1 NOTE Place P1 on the DC Regulator in the TEST position and use the If either of the Output Monitor +5V or -5V Fault LED’s on the DS1 Bar Graph LED’s on each Modulation Encoder to help ColorStat™...
  • Page 97 Section VI - Troubleshooting output is accomplished by turning all PA Modules OFF through b. TRANSIENTS, or other signal pickup, fed back into the modulator action. This occurs in less than 20 milliseconds and transmitter output from the antenna system. may not be noticed by listeners, or will be noticed as a slight c.
  • Page 98 DX-25U 6.27.2.3 Bandpass Filter VSWR Fault Symptom: Higher Than Normal 6.29 Audio Distortion Bandpass Filter VSWR Caused By Problems In The 6.27.2.3.1 Output Network Possible Causes 6.29.1 If a problem occurs in the output network of the transmitter due 6.29.1.1 Failed RF Amplifier(s) to a component failure, the Bandpass Filter VSWR circuit will If audible distortion is heard on the air and the problem is not protect the transmitter until the component can be replaced.

  • Page 99: Improper Overload Settings

    Section VI - Troubleshooting Symptom: Consistent Loss of RF RF amplifier, incorrect MOSFET transistors, or a defective RF 6.30 amplifier output toroid. An RF amplifier that fails from phasing Amplifiers problems will operate for a short time before failure. During this Any type of consistent or repeated failure indicates a problem condition, the module will operate hotter than the other mod- on the RF amplifier or in the location in the transmitter.

  • Page 100: Other Troubleshooting Techniques

    PA Module checked with an ohmmeter. However, there is a requirement FlexPatch™ is a Harris feature to allow the engineer to patch a which restricts the use of some ohmmeters. If the battery voltage failed RF amplifier from an active step position, such as step...

  • Page 101: Using Flexpatch™ For Isolating Modulation Encoder/Rf Amplifier Problems

    Locate RF amplifier RF33 (bottom left RF amplifier). Use URE OF THE RF AMPLIFIER SHOULD THE FlexPatch™ JUMPER a 10x scope probe with an extended tip, Harris part INADVERTENTLY TOUCH ANOTHER COMPONENT ON THE #610-1131-000, and connect it to the anode of CR3 MODULATION ENCODER.

  • Page 102: 6.31.7.1 Excessive Drive Phase Difference

    OPENED TO ACCESS THE RF AMPLIFIER MODULES. waveform. Switch the scope to the X10 position and a. Use a 10x scope probe with an extended tip, Harris part readjust the horizontal position so that the RF transition #610-1131-000, and connect it to TP1 (Q3 drain) on again crosses the center line of the scope.
  • Page 103 Section VI - Troubleshooting a. If the problem follows the module, check the drive phas- c. Insert one end of a FlexPatch™ cable into P8-1. Connect ing, RF drive toroid transformers, and the MOSFET’s. the other end of the jumper to the hole closest to the PA Modules of the jack where the gold jumper was removed.
  • Page 104 DX-25U Figure 6-1 Figure 6-3 Upper Trace - Demodulated audio at 100Hz, 100% Modulation Pin Identification of MOSFET. at 10kW showing missing step due to failed RF Amp. Lower Trace - Modulation Encoder signal for missing step 10. Figure 6-2 Upper Trace - Demodulated audio at 100Hz, 125% + peak, ramp modulation at 10kW showing missing step 56.
  • Page 105 Section VI - Troubleshooting Figure 6-4 Figure 6-6 RF Drive Waveform at RF Amplifier, Gate of Q3 (anode of RF Drain Waveform as seen at RF Amp, Drain of Q3 (TP1) CR3). RF Amplifier turned OFF. (5Vp-p per division) RF Amp turned ON. Shows zero crossing reference phase, and measured phase approximately 4 degrees lagging.
  • Page 106 DX-25U Figure 6-8. FlexPatch™ Operation 6-24 888-2297-002 Rev. R: 11-11-96 WARNING: Disconnect primary power prior to servicing.
  • Page 107 Table 7-0. Replaceable Parts List Index Table 7-1. XMTR, DX 25U ......994 9168 001 Table 7-2.
  • Page 108 DX-25U Table 7-1. XMTR, DX 25U - 994 9168 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 041 1310 013 RUBBER SPONGE 3/8 16.80 FT #SHIPPING TAPE FOR DOOR 358 3131 000 STUD, BRS 1/4-20 X 1 0.0 EA #2C1B (18# EF) (12# GH) (6# JKL)
  • Page 109 994 9165 002 R-BK-DX25U REC BDS KIT 0.0 EA 994 9166 002 R-PK-DX25U REC PTS KIT 0.0 EA 994 9168 002 XMTR, BASIC DX 25U 1.0 EA 994 9210 001 XFMR KIT,STEPDOWN 480/240 0.0 EA 3T001 999 2622 001 HARDWARE LIST, DX50 1.0 EA...
  • Page 110 943 5155 064 HEATSINK SET 1.0 EA 999 2561 001 HARDWARE LIST 1.0 EA Table 7-4. PWA, ANALOG TO DIGITAL CONV - 992 6730 002 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 354 0309 000 TERM SOLDER 22.0 EA TP001 TP002 TP003 TP004 TP005 TP006...
  • Page 111 Section VII - Parts List 382 0081 000 IC, 7406 ESD 1.0 EA U007 382 0159 000 IC, 7407 ESD 2.0 EA U005 U006 382 0359 000 IC, 7815 ESD 1.0 EA U002 382 0360 000 IC, 7915 ESD 1.0 EA U018 382 0472 000 IC, LM318 ESD...
  • Page 112 DX-25U C001 C002 C003 C005 C006 C009 C010 C012 C013 C015 C016 C017 C018 C019 C020 C021 C027 C028 C030 C031 C032 C035 C036 C037 C038 C039 C043 C045 C046 C054 C056 C059 C061 C062 C070 C077 C079 C080 C081 C082 C094 C104 C108 C109 516 0530 000 CAP .01UF 10% 100V X7R...
  • Page 113 929 9009 198 XFMR 1.0 EA T001 999 2760 001 HARDWARE LIST, ANALOG TO 1.0 EA Table 7-5. * MOD ENCODER/BINARY - 992 7089 013 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 382 0159 000 IC, 7407 ESD 1.0 EA U059...
  • Page 114 DX-25U XU017 XU018 XU019 XU020 XU021 XU022 XU023 XU024 XU025 XU026 XU027 XU028 XU029 XU030 XU039 XU040 404 0674 000 SOCKET 14 PIN DIP (D-L) 14.0 EA XU053 XU054 XU055 XU056 XU057 XU059 XU060 XU061 XU062 XU063 XU064 XU065 XU066 XU067 404 0704 000 SOCKET IC 20 PIN 20.0 EA...
  • Page 115 PWB, MOD ENCODER 1.0 EA A014 917 2099 051 FIRMWARE, MOD ENCODER, DX25U 1.0 EA Table 7-6. DRIVER SUPPLY REGULATOR - 992 8006 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 328 0071 000 WASHER, STEEL COMPRESSION 7.0 EA #Q002 #Q003 #Q004 #Q005 #Q006 #Q007...
  • Page 116 922 0922 156 TRANSFORMER 1.0 EA T001 999 2566 001 HARDWARE LIST 1.0 EA Table 7-7. PWA, BUFFER AMP - 992 8038 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 380 0586 000 XSTR, MJE200 ESD 1.0 EA Q001 380 0587 000 XSTR, MJE210 ESD 1.0 EA...
  • Page 117 843 5100 046 PWB, BUFFER AMP 1.0 EA 929 9009 198 XFMR 1.0 EA T001 Table 7-8. DRIVER ENC/TEMP - 992 8048 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 354 0309 000 TERM SOLDER 14.0 EA TP001 TP002 TP003 TP004 TP005 TP006...
  • Page 118 DX-25U 384 0679 000 LED, YELLOW ESD 2.0 EA DS001 DS003 384 0719 000 TRANSZORB 1N6373 5V 5W ESD 2.0 EA CR017 CR018 386 0082 000 ZENER, 1N4744A 15V 1W 5% ESD 4.0 EA CR003 CR004 CR005 CR006 386 0135 000 ZENER, 1N4733A 5.1V ESD 1.0 EA CR014...
  • Page 119 843 5100 093 PWB, DRIVER ENCODER 1.0 EA 999 2569 001 HARDWARE LIST 1.0 EA Table 7-9. OSCILLATOR - 992 8069 002 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 354 0309 000 TERM SOLDER 11.0 EA E001 E002 E003 E004 TP001 TP002 TP003...
  • Page 120 843 5155 032 PWB, OSCILLATOR 1.0 EA 999 2450 002 HARDWARE LIST 1.0 EA Table 7-10. CONTROLLER BOARD - 992 8071 002 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 354 0309 000 TERM SOLDER 8.0 EA TP001 TP002 TP003 TP004 TP005 TP006...
  • Page 121 Section VII - Parts List 380 0673 000 XSTR, NPN D44H8 ESD 1.0 EA Q004 380 0678 000 XSTR, ARRAY QUAD 2222 ESD 6.0 EA Q003 Q005 Q006 Q007 Q009 Q010 382 0082 000 * IC 7420 4.0 EA U002 U014 U026 U057 382 0309 000 IC, SN74LS08N ESD 2.0 EA...
  • Page 122 DX-25U #U045 #U046 #U047 #U048 #U054 #U056 #U061 410 0405 000 INSULATOR XSTR TO220 3.0 EA #Q001 #Q002 #Q004 506 0242 000 CAP .068UF 63V 5% 1.0 EA C025 506 0246 000 CAP .47UF 63V 5% 1.0 EA C041 516 0453 000 CAP .1UF 100V 20% X7R 67.0 EA C001 C002 C003 C004 C005 C006 C007 C008...
  • Page 123 843 5400 091 SCH, CONTROLLER 0.0 EA 843 5400 093 PWB, CONTROLLER 1.0 EA Table 7-11. LED BOARD - 992 8072 002 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 358 1928 000 JUMPER 1/4 LG 1/8H 6.0 EA JP001 JP002 JP003 JP004 JP005 JP006 358 2177 000 SPACER, LED MOUNT .380 LG...
  • Page 124 DX-25U 382 0770 000 IC, 74HC04 ESD 5.0 EA U007 U039 U041 U048 U049 382 0771 000 IC 74HC08 ESD 12.0 EA U006 U009 U016 U020 U022 U023 U025 U031 U034 U045 U064 U065 382 0774 000 IC 74HC14 ESD 5.0 EA U004 U021 U026 U046 U066 382 0777 000...
  • Page 125 Section VII - Parts List C122 C124 C126 C127 C130 C134 C135 C136 C137 C138 C139 C140 C141 C142 C144 C145 C147 C149 C150 C152 C153 C154 C155 C156 C157 C159 516 0511 000 CAP 0.47UF 100V 20% 39.0 EA C013 C014 C018 C021 C022 C023 C026 C027 C029 C032 C033 C039 C044 C047 C048 C052 C053 C057...
  • Page 126 DX-25U 548 2400 381 RES 6.81K OHM 1/2W 1% 1.0 EA R033 548 2400 394 RES 9.31K OHM 1/2W 1% 1.0 EA R107 548 2400 401 RES 10K OHM 1/2W 1% 41.0 EA R020 R021 R022 R026 R031 R032 R036 R044 R048 R050 R056 R059 R064 R069 R089 R091 R095 R097 R111 R123 R128 R129 R131 R133 R139 R143 R144 R145 R157 R159 R171 R174...
  • Page 127 Section VII - Parts List Table 7-12. ANALOG INPUT - 992 8077 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 335 0262 000 DF137A INSULATING WASHER 2.0 EA #Q005 #Q006 380 0126 000 XSTR, PNP 2N4403 ESD 2.0 EA Q001 Q002...
  • Page 128 DX-25U C039 C042 C055 C065 516 0774 000 CAP 56PF 5% 100V C0G 5.0 EA C013 C014 C015 C020 C034 516 0891 000 CAP 0.100UF 10% 50V 2.0 EA C091 C093 522 0554 000 CAP 4.7UF 50V 20% 4.0 EA C073 C078 C079 C081 526 0048 000 CAP 10UF 20V 20%...
  • Page 129 0.0 EA 843 5100 067 PWB, ANALOG INPUT 1.0 EA 999 2610 001 HARDWARE LIST 1.0 EA Table 7-13. OUTPUT SAMPLE - 992 8203 003 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 358 1928 000 JUMPER 1/4 LG 1/8H 1.0 EA JP004...
  • Page 130 DX-25U 382 0856 000 IC 74HC4078 ESD 1.0 EA U009 382 1048 000 * IC, UC3834N ESD 2.0 EA U013 U015 382 1084 000 IC, LP339N ESD 2.0 EA U014 U016 382 1171 000 IC 74HC540 (ESD) 1.0 EA U007 382 1211 000 IC ICL7136 ESD 1.0 EA...
  • Page 131 Section VII - Parts List C021 C029 C062 C071 C084 C085 C086 C087 C088 C089 C090 C091 526 0314 000 CAP 33UF 10V 20% 1.0 EA C046 526 0378 000 CAP 1UF 50V 20% 2.0 EA C034 C055 540 1380 000 RES NETWORK 10K OHM 2% 3.0 EA R015 R069 R071...
  • Page 132 843 5100 091 PWB, DC REGULATOR 1.0 EA 999 2681 002 HARDWARE LIST FOR DC 1.0 EA Table 7-15. OUTPUT MONITOR - 992 9298 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 000 0000 003 FREQUENCY DETERMINED PART 4.0 EA C005 C041 L003 L009...
  • Page 133 Section VII - Parts List 500 0841 000 CAP, 750PF 300V 5% 1.0 EA C020 500 0854 000 CAP, VAR, 300-1000PF 175V 6.0 EA C006 C015 C016 C021 C029 C040 500 0878 000 CAP, MICA, 1500PF 500V 5% 2.0 EA C028 C030 500 0903 000 CAP, MICA, 2700PF 500V 5%...
  • Page 134 L011 939 6208 260 SHIELD 1.0 EA #A027 999 2496 001 HARDWARE LIST 1.0 EA Table 7-16. XMTR, BASIC DX 25U - 994 9168 002 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 917 2501 007 KIT, WIRE 162 1.0 EA 992 7090 002 PA CABINET, DX 25U 1.0 EA...
  • Page 135 Section VII - Parts List 384 0839 000 RECT 1000PIV 300A 1N4056 ESD 12.0 EA CR001A CR003A CR005A CR007A CR009A CR011A CR001B CR003B CR005B CR007B CR009B CR011B 384 0840 000 RECT 1000PIV 275A 1N4056R ESD 12.0 EA CR002A CR004A CR006A CR008A CR010A CR012A CR002B CR004B CR006B CR008B CR010B CR012B 398 0433 000...
  • Page 136 DX-25U 552 0358 000 RHEO 25 OHM 75 W 1.0 EA R002 552 0402 000 RHEO 5 OHM 150 W 1.0 EA R001 560 0077 000 VARISTOR 275VRMS 30KA 2.0 EA RV001 RV002 574 0461 000 RELAY DPDT 10A 24VAC COIL 1.0 EA K003 604 1079 000...
  • Page 137 PWA, BUFFER AMP 1.0 EA A016 992 8048 001 DRIVER ENC/TEMP 1.0 EA A019 992 8056 002 PA CAB CABLE PKG, DX 25U 1.0 EA 992 8058 001 CABINET PKG 1.0 EA 992 8059 001 0.125 AL SM FAB PKG 1.0 EA 992 8059 002 PKG, FAB, 0.090 AL SM...
  • Page 138 DX-25U 999 2589 002 HARDWARE LIST, PA CABINET 1.0 EA Table 7-18. GROUND HOOK ASSY - 938 4203 020 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 254 0017 000 WIRE, ROPE 10AWG 0.950 FT 296 0019 000 PLASTIC TUBE 4AWG CLEAR 0.850 FT...
  • Page 139 Section VII - Parts List 382 0781 000 IC, 74HC74 ESD 1.0 EA U011 382 0791 000 IC, 74HC138 ESD 1.0 EA U008 382 0800 000 IC, 74HC161 ESD 1.0 EA U006 382 0882 000 IC, 78L05A ESD 1.0 EA U012 382 1043 000 IC UDN2595 ESD...
  • Page 140 DX-25U 843 4038 201 PWB, SWITCH/METER 1.0 EA Table 7-22. PWA, PWR DISTRIBUTION,ESD SAFE - 992 6916 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 610 1027 000 HEADER, MALE 12 PIN 7.0 EA J001 J002 J003 J004 J005 J006 J007...
  • Page 141 7.0 EA T2/T15 T3/T14 T4/T13 T5/T12 T6/T11 T7/T10 T8/T09 999 2571 001 HARDWARE LIST 1.0 EA Table 7-25. PWA, COMB MOTHERBD, ESD SAFE - 992 7088 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 324 0257 000 NUT, CAPTIVE 6-32 4.0 EA...
  • Page 142 843 5100 029 PWB, FUSE 1.0 EA A025 999 2576 002 HARDWARE LIST 1.0 EA Table 7-28. PA CAB CABLE PKG, DX 25U - 992 8056 002 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 917 2099 003 MAIN CABLE DX-50 1.0 EA...
  • Page 143 CABINET END PNL 1.0 EA 843 5100 016 ASSY INSTR, DX50 PA & OUT 0.0 EA Table 7-30. EXTERNAL INTERFACE - 992 8070 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 380 0678 000 XSTR, ARRAY QUAD 2222 ESD 9.0 EA...
  • Page 144 843 5100 063 PWB, EXTERNAL INTERFACE 1.0 EA 999 2455 002 HARDWARE LIST 1.0 EA Table 7-31. PWA, NEUTRALIZATION, ESD SAFE - 992 8079 002 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 051 0001 023 *ADHESIVE, DP-190 GRAY 0.0 EA 546 0295 000 RES 50 OHM 3.25W 5%...
  • Page 145 MTR O-50KW, 4-1/2", W 1.0 EA M003 638 0025 000 SHUNT METER 250A 50MV 1.0 EA SH001 646 1464 000 INSERT, DX 25U NAMEPLATE 1.0 EA 922 0922 209 FILTER BRACKET 1.0 EA 992 7087 003 COMB MOTHERBD BINARY, ESD SAFE 1.0 EA...
  • Page 146 DX-25U Table 7-37. XFMR PKG (BINARY MBD) - 992 7096 001 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 922 0922 002 XFMR PAIR 2.0 EA T8/T9 T7/T10 922 0922 003 XFMR PAIR 1.0 EA T1/T16 922 0922 004 XFMR PAIR 2.0 EA...
  • Page 147 ADPT BNC UG492A/U 1.0 EA J001 646 1347 000 MARKER STRIP 3 TERM 1.0 EA #TB001 646 1462 000 NAMEPLATE, HARRIS 10.5 LG 1.0 EA 648 0051 000 * COUNTER CCW 2.0 EA 650 0150 000 KNOB RD PLAIN SKIRT 2.0 EA...
  • Page 148 DX-25U Table 7-40. GROUND HOOK ASSY - 938 4203 021 HARRIS P/N DESCRIPTION QTY/UM REF. SYMBOLS/EXPLANATIONS 252 0017 000 WIRE, STRD 26 AWG WHT 4.30 FT 296 0019 000 PLASTIC TUBE 4AWG CLEAR 4.250 FT 306 0006 000 NUT, HEX 10-32 2.0 EA...
  • Page 149 Section VIII - Diagrams Section VIII Diagrams Introduction This section provides a list of the drawings provided in the separate drawing package. Drawings Provided Under Separate Cover Drawing Description Drawing Number Schematic, Switch Board/Meter Board 839 6208 301 Schematic, RF Multimeter 839 6208 302 Schematic, Driver Supply Regulator 839 7855 004...
  • Page 150  ...

  • Page 151: Principles Of Operation

    Section A Oscillator (A17) Buffer/Squaring Amplifier Introduction A.4.3 Buffer amplifier Q2 is coupled to the oscillator output, and This section includes a description of the Oscillator and trou- operates as an overdriven amplifier, with a +5 VDC supply bleshooting information. voltage.
  • Page 152 DX-25U plifier stage is turned on. Use S4 on the LED Board to check the sample from the output network. The oscillator sync is adjusted output of U4. with DIP switch S1 and inductor L4. CMOS switch U4 A.5.1.2.1 The Output Current sample from T6 at the combiner output is Observe the DC voltage at U4-6 while depressing S4 on the LED brought into the Oscillator at J3-1.
  • Page 153 Section A - Oscillator (A17) U5 faulty A.5.1.3.5 Symptom: Output At Incorrect Frequency A.5.4 The output of U5-7 should be 4-4.5 Vp-p square wave, and can A.5.4.1 Possible Cause: Frequency Divider Jumper Plug P2 be checked at P3-3. Check the position of the P2. The crystal frequency will be Symptom: No RF Output, External Oscillator A.5.2 divided by four if P2 is from 1-2, and will be divided by eight if...
  • Page 154 DX-25U Table A-2. Oscillator Board A17, Controls and Indicators LOCATION COMPONENT FUNCTION/DESCRIPTION Adjusts the frequency of crystal Y1. Adjusts the frequency of crystal Y2. Fuse in +22 Volt unregulated input for +15 Volt and +5 Volt regulators. Protects -22 Volt supply if a -15 Volt regulator fault occurs. Input for external frequency source (e.g.
  • Page 155 Section B Buffer Amplifier (A16) Output Coupling Network Introduction B.2.5 The output of the Q3-Q4 amplifier stage is coupled to the This section includes a description of the Buffer Amplifier, and Predriver input through broad-band coupling network C3, R8- troubleshooting information. The Buffer Amplifier plugs into the R11 and L2.
  • Page 156 DX-25U Back-to-back zener diodes CR3 and CR4 should indicate a low P4-8 and 9; this indicates that the coaxial cable and connectors leakage current in either direction; if one of the diodes is shorted, are good. they will look like a single diode with an ohmmeter check or Symptom: Buffer Amplifier LED on Color- B.3.2 “diode test”...
  • Page 157 Section B - Buffer Amplifier (A16) Table B-1. Buffer Amplifier Controls and Indicators LOCATION COMPONENT FUNCTION/DESCRIPTION Pre-driver A, Fuse Indicator. When illuminated, indicates open fuse A16F1. Pre-driver B, Fuse Indicator. When illuminated, indicates open fuse A16F2. Buffer Amp Fuse Indicator. When illuminated, indicates open fuse A16F3. A16F1 Pre-driver Section A FUSE.
  • Page 158  ...
  • Page 159 Section C RF Amplifier Introduction is off (cut off). When the upper pair is off the lower pair is on. The output is switched between ground (about zero Volts) and This section includes a description of the RF amplifier module, the positive supply voltage at an RF rate.
  • Page 160 DX-25U Figure C-1. RF Amplifier Module, Simplified Diagram (817 2099 031) Figure C-2. RF Amplifier Operation, Half-Quad Configuration (817 2099 032) Figure C-3. RF Amplifier Operation, Full Quad Configuration (817 2099 033) 888-2297-002 WARNING: Disconnect primary power prior to servicing.
  • Page 161 Section C - RF Amplifier Modules Figure C-4. RF Amplifier Module, Control Section Operation (817 2099 034) A TTL “LOW” control signal from the Modulation Encoder will This explanation is based on simplified diagram, Figure C-5. switch PNP transistor Q5 ON and switch NPN transistor Q7 OFF. When the polarity of the induced voltage in the combiner trans- A TTL “HIGH”...
  • Page 162 DX-25U Figure C-5. RF Amplifier Module: Combiner Transformer Primary Winding Current Flow With Module Off (817 2099 035) VDC for the “BIG STEP” PA Modules; +115 VDC and +60 VDC section fails the drive to the other section will not be affected. A for “BINARY”...
  • Page 163 Section C - RF Amplifier Modules When the amplifier is turned ON, Q5 and Q6 and diodes CR5 circuit are immune to this damage. The MOSFET transistors are and CR6 provide conduction paths for the RF drive signal. shipped in antistatic packaging. The transistors should remain in this packaging until they are to be used or tested.
  • Page 164 DX-25U • Are the A and the B halves of the amplifier receiving the Solder transistor leads and trim. • proper drive? Replace blown fuse(s). Is the amplifier receiving a proper ON/OFF control signal C.4.1.2 Checking RF Module Operation from the Modulation Encoder? The most common method of troubleshooting an RF amplifier Did something short at the output of the amplifier? after a failure is to put the repaired amplifier in a known working...
  • Page 165 Section C - RF Amplifier Modules Table C-1. RF Amplifier Module Boards Controls and Indicators LOCATION COMPONENT FUNCTION/DESCRIPTION Illuminates when fuse F1 is open and when there is a short circuit failure, or when the power MOSFETs try to conduct supply voltage when the amplifier is switched ON. Illuminates when fuse F2 is open and when there is a short circuit failure, or when the power MOSFETs try to conduct supply voltage when the amplifier is switched ON.
  • Page 166  ...
  • Page 167 Section D Driver Combiner/Motherboard (A14) Introduction output from the splitter reenters the board at J17 through J20 to drive the 14 Driver Modules. This section includes a description of the Driver Com- biner/Motherboard. The Predriver supply voltage from the +60 VDC supply goes through rheostat R1 and enters the board at J28-2.
  • Page 168 DX-25U transformer T10 is a torroidal transformer located between the Driver Combiner/Motherboard and the RF Drive Splitter. 888-2297-002 12-12-94 WARNING: Disconnect primary power prior to servicing.
  • Page 169 Section E Driver Supply Regulator (A22) +15 Volt Regulator Introduction E.4.1 A 3-terminal integrated circuit voltage regulator, U1, provides This section includes a description of the Driver Supply Regula- the +15 Volt supply for U2. tor, and troubleshooting information. The Driver Supply Regulator assembly includes a printed circuit Control +VDC Reference E.4.2 board and a heat sink.
  • Page 170 DX-25U the drain current and decrease the effective source-to-drain “re- Q2’s drain voltage and regulator output voltage “A” is divided sistance.” An input voltage of less than +10 Volts will effectively by the voltage divider consisting of R22, R24, and R25. As Q2 “saturate”...
  • Page 171 Section E - Driver Supply Regulator (A22) Figure E-1. Driver Supply Regulator Simplified Schematic Diagram (817 2099 028) protect the MOSFETs against excessive source-to-gate voltage. the resistor is measured. Resistors R44 and R45 are voltmeter Diode CR15 protects the regulator circuit against negative tran- multiplier resistors.
  • Page 172 DX-25U The operation of the Driver Supply Regulator is also dependent on supply components, cabling, and on the Driver Supply Regulator. the operation of the AUTO module from the Driver Encoder/Temp If F10 is good, check for loose connector or other open circuit Sense Board.
  • Page 173 Section E - Driver Supply Regulator (A22) NOTE The voltage at U2-1 should vary when CLOSED LOOP AD- JUST Control R12 is varied over its range. If the setting of R12 is changed, refer to the section on setting RF drive in the Tuning/Frequency Change Procedure in SECTION V, Maintenance, for proper adjustment of RF drive.
  • Page 174  ...
  • Page 175 Section F RF Multimeter (A23) Introduction DC current path. One side of the meter is grounded through a section of switch S1 for Driver stage voltage measurements. The This section describes the RF Multimeter board. meter is isolated from ground for current measurements. The RF Multimeter provides metering of the Predriver and The RF Multimeter positions are defined and detailed in the Driver sections of the transmitter.
  • Page 176  ...
  • Page 177 Section G RF Combiners: Binary Combiner/Motherboard (A1) and Main Combiner/Motherboards (A2 through A4) Introduction will provide twice the VOLTAGE across the combiner and there- fore twice the RF output voltage. This section includes a description of the Main and Binary Combiner/Motherboards.
  • Page 178 DX-25U all active amplifiers deliver combinations of equal and binary In addition, four of the Binary steps (1/2, 1/4, 1/8, and 1/16) have tapped transformer primary windings for fine adjustments in step weighted RF voltages. amplitude. The tap positions depend on operating frequency and G.2.2.1 Binary Steps are selected with P30, P31, P32, and P33.
  • Page 179 Section H Output Sample Board (A26) and Output Monitor (A27) H.2.1.3 Calibration Jumpers Introduction Plugs P1 and P2 and jumper JPR4 are used to calibrate the VSWR This section includes circuit descriptions and troubleshooting circuits on the Output Monitor. information for the Output Sample Board and Output Monitor. The Output Sample Board contains circuits to sample RF voltage Output Monitor H.2.2...
  • Page 180 DX-25U Figure H-1. Phase Angle Detector, Simplified Diagram (817 2099 038) winding and a voltage will be induced in the secondary winding. through L8 and C12, C39 and C47. Switch S7 is used to select A full-wave rectifier will then produce a DC output voltage at coarse values of inductance and capacitance.
  • Page 181 Section H - Output Sample (2A26) & Output Monitor (1A27) comparator output will go LOW. Diodes CR11 and CR13 protect the “Bandpass VSWR trip” C49 and R50 at U6-7 provide a 19 U1 from transient voltages. millisecond pulse width. Switch S5 prevents U6 from generating a pulse during phase R-C Network H.2.2.5.2 angle detector circuit adjustments.
  • Page 182 DX-25U H.2.2.12 +5 VDC And -5 VDC Regulators lation monitor at LOW power is adjusted by the tap on L7. When DC supply inputs to the Output Monitor are +8 VDC and -8 VDC, the transmitter is in the MEDIUM or HIGH power position, the from the low voltage power supply.
  • Page 183 Section H - Output Sample (2A26) & Output Monitor (1A27) Table H-1. Output Monitor Board A27, Controls and Indicators See Figure H-2 COMPONENT FUNCTION/DESCRIPTION Balances (nulls) Forward Power directional coupler section. Balances (nulls) Reflected Power directional coupler section. Ant. VSWR detector, Fine Isolation Adjust. Adjusted for maximum isolation between current sample and voltage sample.
  • Page 184 DX-25U Table H-2. Output Monitor Board A27, Test Points See Figure H-2 COMPONENT FUNCTION/DESCRIPTION Antenna phase angle detector, voltage sample, used during phase angle detector adjustment. Antenna phase angle detector, current sample, used during phase angle detector adjustment. Bandpass Filter phase angle detector, voltage sample, used during phase angle detector adjustment. TP10 Bandpass Filter phase angle detector, current sample, used during phase angle detector adjustment.

  • Page 185: Maximum Power Adjust (U7, R27)

    Section J Analog Input Board (A35) Introduction If you do not know the source impedance use either J1 or J2. If the source impedance is greater than the input impedance, some This section includes a description of the Analog Input Board overshoot will result.
  • Page 186 DX-25U Analog Divider (U10) J.2.6 audio signal will also change proportionally with the DC com- ponent. The Analog Divider IC U10 compensates for variations in the +230 VDC supply and reduces hum and noise. If the feedback J.2.7.1 BCD Logic Input To U8 voltage from the +230 VDC supply increases, the output from The BCD power control signal is generated on the Controller and the analog divider will decrease.
  • Page 187 Section J - Analog Input (A35) Square Wave Generator U19 J.2.9.1.1 A “PA Turn Off-H” signal is generated by the Controller during Differential amplifier U19 operates “open loop,” so its gain is fault protection and when the transmitter is turned OFF. This very high.
  • Page 188 DX-25U Digital Control Signal at U8 is Zero J.4.1.1.2 Refer to SECTION M, DC Regulator, for a further description There are several possible causes, including: of these voltage regulator circuits. a. BCD (Binary Coded Decimal) Control Signal from Con- Refer to SECTION Q, LED Board, for a further description of troller A38 is Zero.
  • Page 189 Section J - Analog Input (A35) Table J-2. Power Level Coding the fault line output is LOW, but the voltage at the Test Point is good, then the regulator IC is defective. If the fault line is output HIGH but there is still a Power Level Decimal BCD (Binary Coded...
  • Page 190 DX-25U Table J-3. Analog Input Board A35, Controls and Indicators LOCATION COMPONENT FUNCTION/DESCRIPTION Protects +22 V supply from +15 Volt regulator faults. Protects -22 V supply from -15 Volt regulator faults. Audio Gain Adjust. Adjusts audio input sensitivity (audio input level required for 100% modulation).
  • Page 191 Section K Analog To Digital Converter (A34) Introduction quency change procedure in Section 5, Maintenance for infor- mation on setting S1). This section describes the Analog to Digital Converter board and includes a “silkscreen” of component locations. Schmitt Trigger U12C converts the RF input to TTL level pulses. Diodes CR14 and CR15 limit the voltage at the Schmitt trigger’s The schematic diagram can be found in the Drawing Package and input to between +0.7 and +4.3 Volts.
  • Page 192 DX-25U Error Detecting Circuits The analog signal level at the board’s input is high so that any K.3.5 noise pickup on interconnecting cables does not degrade the There are circuits on the A/D board that determines if the clock signal-to-noise ratio. Inverting amplifier U28 has a gain of 0.5 to signal is being received and if the A/D converter is working provide the proper single level to the A/D chip input and also properly.
  • Page 193 Section K - Analog to Digital Converter (A34) K.3.7.2 Amplifier Stage (U24, U25, U26) re-trigger and the output will remain 1. If the pulses stop or the The output of the A/D converter is amplified by U24 and U25. frequency is too low the one-shot output will go low. The gain of the amplifier stage is slightly over 5.
  • Page 194 DX-25U Symptom: ColorStat™ panel CONVERSION ment which can introduce noise and cause errors in measure- K.5.1 ment. ERROR Indicator is RED, transmitter oper- ates normally. K.3.8.4 Voltage Regulators (U2, U16, U18, U19, U20, U21, Q1) Four regulated voltages are provided by on-board regulators. U2 If the transmitter operates normally, but there is a CONVER- is a 7815 which converts 22 V to 15 V.
  • Page 195 Section K - Analog to Digital Converter (A34) Troubleshooting the Frequency Divider K.5.2.3.1 K.5.2.5 POWER UP RESET-L FAULT The Synchronous Binary Counter, U29, divides the input by four Measure the voltage at U12-13. There should be a +5 VDC signal present when the Low Voltage is ON.
  • Page 196  ...
  • Page 197 Section L Modulation Encoder (A37) Introduction d. B10 = 1/16 Step e. B11 = 1/32 Step This section includes a description of the Modulation Encoder and troubleshooting information. f. B12 = 1/64 Step If the status of B7 through B12 is: Refer to SECTION V, Maintenance, for maintenance and re- placement procedures.
  • Page 198 DX-25U L.3.1.2 Modulated B- Supply VDC) and the emitter of the “pull-down” (current sink) transistor The Modulated B- Supply is brought into the board at J19-1 and is connected to the V- terminal (Gnd). Only one transistor is is applied to the outputs of the driver IC’s through pull-down turned on at a time, so that the output is pulled to B+ or Gnd.
  • Page 199 Section L - Modulation Encoder (A37) generates a fault, the ColorStat™ panel “Modulation Encoder force U53-8 LOW. This drives U59-4 LOW to produce the CABLE INTERLOCK” LED will illuminate red. Refer to the “PAOFF-L” signal on the A37 Modulation Encoder at J18-8. interlock chart on sheet four of the Mod Encoder Schematic to Inverter U56-4 goes to a logic HIGH which drives U53-8 to logic identify the RF amplifier numbers monitored by each interlock...

  • Page 200: Clip Circuit

    DX-25U resistor and the 30K resistor and diode CR11 or CR12 on the RF A “CLIP” patch cable is used to jumper P15 to the first unused amplifier. “Big Step” latch output. If the A/D converter attempts to turn this unavailable step ON, the line will go HIGH and drive inverter The voltage level at U62-7 will drop below the voltage at U62-6 U57-9.
  • Page 201 Section L - Modulation Encoder (A37) connected between the Inverter/Driver input and P9-1 or 2, the diagram of PA Turn-Off logic, Figure L-3, and to the Schematic “Momentary Test” button can be depressed to turn that module Diagram for PA Turn-Off logic). Most causes of “PA Off”...
  • Page 202 DX-25U Figure L-2. Mod Encoders Interconnect Diagram Figure L-3. 888-2297-002 Rev. T2: 06-27-97 WARNING: Disconnect primary power prior to servicing.
  • Page 203 Section L - Modulation Encoder (A37) Figure L-4. Cable Interlock & RF Amp Fault Indicator Rev. T2: 06-27-97 888-2297-002 WARNING: Disconnect primary power prior to servicing.
  • Page 204 DX-25U L.5.3.3 Possible Cause: Cable From Modulation Encoder L.5.3.4 Possible Cause: Printed circuit board fault or con- to a Combiner/Motherboard is not connected, or nector damage connector plug loose in socket These are unlikely, but careful visual inspection could show a Check cable connectors to determine that all are plugged in and printed circuit board fault (short, damaged pc board trace, poor properly seated in the printed circuit board sockets.
  • Page 205 Section L - Modulation Encoder (A37) Table L-1. Modulation Encoder, Controls & Indicators LOCATION COMPONENT FUNCTION/DESCRIPTION When illuminated, indicates a Cable Interlock Error, (1 thru 8), PA OFF, Blown Fuse. Fuse F1 +5 volt supply fuse. B1-B8 P1 thru P8 Used for FlexPatch™...
  • Page 206  ...
  • Page 207 SECTION M DC REGULATOR (A30) M.2.2.1 Other Supplies Using the UC3834 Introduction This IC is also used in on-board regulated supplies on other This section describes the DC Regulator, and includes trou- printed circuit boards in the transmitter. Additional regulated bleshooting information.
  • Page 208 DX-25U IC’s internal driver amplifier provides base current for the exter- This protects the IC from over-dissipation. The under-voltage will then cause a “Fault Alert” to be generated. nal series pass transistor, at the “Driver Sink” for positive sup- plies, or at the “Driver Source” for negative supplies. If the B+ (+5.75 VDC) Regulated Supplies (DC M.2.3 supply output voltage increases, the regulator IC decreases base...
  • Page 209 Section M - DC Regulator (A30) in different supplies. Also, the +15 VDC supplies do not have the pares the pre-distorted reference voltage, at pin 9, and a sample “Start Up” circuit used in the +5 VDC supplies. of the supply output voltage at pin 8. The regulator IC controls the base current into series pass transistor Q2 to adjust the output Modulated B- Supplies M.2.4...

  • Page 210: Fault Detection Circuits

    DX-25U +5 VDC Supply M.2.11.2 B+ Fault Detector M.2.8 IC U4 will produce a B+ Fault output if the B+ voltage drops The DC Regulator fault sense circuitry is operated from a regu- below 15% or rises above 10% of normal. Pin 7 (TP13) of U4 lated +5 VDC supply consisting of regulator U11.

  • Page 211: Troubleshooting

    Section M - DC Regulator (A30) The switch positions for the meter are as follows: c. Read LCD Multimeter reference voltage • Once the fault is isolated to an individual circuit, troubleshoot • possible causes. B +8V IN (2) • B B+ OUT (3) M.3.1.1 +22V Fault •...
  • Page 212  ...

  • Page 213: Introduction

    Section N External Interface (A28) Introduction Each TYPE of interface circuit is described in the following paragraphs. Sheet three of the schematic diagram provides a This section describes the External Interface, and includes trou- summary of information for each type of interface circuit, in the bleshooting information.
  • Page 214 DX-25U Figure N-3. Equivalent Circuits, For Calculating Effect of Circuit Loading Figure N-1. External Interface, on “Monitor Voltage” Outputs Typical Status Output Circuits (817 1280 086) (817 1280 088) Figure N-2. External Interface, Typical Control Input Circuits (817 1280 087) 888-2297-002 12-12-94 WARNING: Disconnect primary power prior to servicing.

  • Page 215: Monitor Voltage Outputs

    Section N - External Interface (A28) N.3.2.1 Opto-isolator complete schematic diagrams. There are six different parameters The opto-isolator input is a light-emitting diode, with both sides using this type of monitor voltage output: above ground. When current flows, an internal LED illuminates a.

  • Page 216: External Interface Power Supplies

    DX-25U N.3.7.1 “PA TURN OFF” Troubleshooting The “PA TURN OFF” control input turns off all PA Modules through the modulation section of the transmitter. It does NOT Symptom: No Remote Control Inputs Operate N.4.1 turn off the +230 VDC PA Power Supply. N.4.1.1 Possible Cause: Supply voltage for External Inputs The “PA TURN OFF”...
  • Page 217 Section N - External Interface (A28) N.4.5.2 Possible Cause: Shorted Transistor switch), the corresponding terminal should be LOW, because the The status interface transistors are in DIP integrated circuit transistor on the External Interface provides a current sink to packages; pin-outs are shown on the External Interface sche- ground.
  • Page 218  ...

  • Page 219: Introduction

    Section P Controller (A38) Introduction REMOTE inputs. The transmitter’s fault and overload sections can generate OFF commands, VSWR induced LOWER com- This section describes the Controller. Topics include Function, mands, or temperature induced LOWER Power commands. Location, Block Diagram Description and Circuit Descriptions. The transmitter turn-on/turn-off control logic provides drive The description is divided into functional groups of circuits, as signals for step-start relays K1 and K2 and also provides logic...
  • Page 220 DX-25U LOW “Inverted Turn-on Pulse” is generated at the Q-not The 1.6 second “K1 TURN-ON” pulse will continue to output and generates a “Data Strobe” signal for the Analog remain HIGH for approximately 0.4 seconds, then it will Input Board data latches. go LOW, K1 Drive will be removed, and K1 will de-ener- gize.
  • Page 221 Section P - Controller (A38) Figure P-1 Block Diagram Turn-On/Rurn-Off Control Logic Rev. S: 05-02-97 888-2297-002 WARNING: Disconnect primary power prior to servicing.

  • Page 222: Transmitter Power Control Logic

    DX-25U P.4.1.3 TYPE 1/TYPE 2 FAULT Inputs g. INHIBIT GATES: The inhibit gates prevent the LOW, These inputs generate an “INHIBIT K2-L” signal at U52-8 and MEDIUM or HIGH command from generating a “TURN cause the same circuit action as described for “Transmitter ON REQUEST”...
  • Page 223 Section P - Controller (A38) ceived from the Power Control logic, but U56A is inhibited at e. Inhibits K2. This will de-energize the K2 contactor if the pin 1 by the “K2 IS CLOSED-H” signal. There are no other transmitter is ON. signal changes in the turn-on/turn-off control logic and no contactors operate.

  • Page 224: Turn-On

    DX-25U P.5.1.3 INHIBIT: B” signal which resets the “Underdrive Fault” detector. Refer The one-shot is INHIBITED if the “A” input is HIGH, or the to Section Q, LED Board, for a description of Underdrive Fault “CLEAR” input is LOW. The following conditions INHIBIT circuits.

  • Page 225: Pa Turn-Off (U53-3, U52-6, And S2)

    Section P - Controller (A38) PA Turn-off (U53-3, U52-6, and S2) P.5.5 MOTE switch is in the LOCAL position). The opto-isolator output is paralleled with the corresponding Local Control input The PA Turn-off circuit generates a logic LOW output at U53-3. transistor.

  • Page 226: Power Level Change" Pulse

    DX-25U Inverters (U41-2/4/6/8/10/12) P.6.3.1 Priority Encoder and Decoder: Circuit Description P.6.3.1.6 The priority encode circuit uses an eight-to-three line Priority All six Decoder outputs are inverted by the six sections of Hex Encoder (U44), a three-to-eight line decoder (U42), and three Inverter U41.

  • Page 227: Power Level Latch Outputs

    Section P - Controller (A38) a. The trigger input of “Decode Inhibit” one-shot U56-10 to 1. The Step-start sequence begins inhibit the decoder for .25 seconds and prevent transmitter 2. The Oscillator output is switched ON turn-on during that time. 3.
  • Page 228 DX-25U Figure P-3 Block Diagram Power Control Section P-10 888-2297-002 Rev. S: 05-02-97 WARNING: Disconnect primary power prior to servicing.

  • Page 229: Data Strobe Gates (U1-3/8/11 And U13-8)

    Section P - Controller (A38) count “up” input of the next counter. For the “one’s” counter, The clock pulse train alternates between HIGH and LOW states. the carry increments the “ten’s” counter one digit; the “ten’s” Clock pulses will appear at a gate’s output only when: carry output increments the “hundred’s”...
  • Page 230 DX-25U Figure P-4. Controller Board, Command Input Circuit 817 2099 027 If the first bit and the last bit are BOTH HIGH, the decimal digit Decimal BCD Bits: must be a “9”. To identify “999”, six bits must be checked. Number H1-H4 For the High power mode BCD output, these are bits H1 and...

  • Page 231: Clock Inhibit Gate (U1-6)

    Section P - Controller (A38) Only one buffer output for each bit is active at any time; the a. RAISE, LOWER, HIGH, MEDIUM, LOW status: Logic HIGH inputs illuminate indicator lamps in the buttons on other two will be in the high impedance “off” state. All three the transmitter front panel.

  • Page 232: Interlock Status Logic: Inputs

    DX-25U b. External Interlock (Logic HIGH if “Fault”) c. Interlock String (Logic LOW if “Fault”) P.7.1.1 Door Interlock Input Door interlocks include the Driver Compartment inner access door, the Center Control Compartment RF Amp inner access door and the Left Control Compartment RF Amp inner access door. When all doors are closed, the door interlock switches ground the “Door Interlock”...
  • Page 233 Section P - Controller (A38) Figure P-7. Controller Board, Interlock Status Logic Simplified Diagram (817 2099 026) Rev. S: 05-02-97 888-2297-002 P-15 WARNING: Disconnect primary power prior to servicing.

  • Page 234: Interlock Status Logic: Outputs

    DX-25U lock inputs. If the +30 Vdc supply fails, an Interlock Fault output R56 and R58. The input to U50-9 is HIGH and U50-8 is LOW. is generated which turns the transmitter OFF. The pulse stretcher “B” input U61-10 is LOW, and the “Q” output U61-5 is LOW.

  • Page 235: Interlock String Operation

    Section P - Controller (A38) Figure P-8. Control Board "Supply Fault" (“Regulator Fault”) Circuit, Simplified Diagram (817 1280 097) will bring U60-4 LOW. The LOW input to U60C will force “Door Interlock” status indication. When an “External Interlock U60-10 HIGH. fault-H”...

  • Page 236: Power Supplies

    DX-25U Power Supplies NOTE Do not install back-up batteries unless C44 is charged (+5B On-board regulators supply +5 Vdc for all logic circuits on the voltage at TP6 is greater than 4.5 Volts). Current drain from the Controller, and +15 Vdc and -15 Vdc for the analog meter batteries into C44 will shorten battery life.

  • Page 237: Data Clear-L" Signal

    Section P - Controller (A38) Supply Fault logic outputs LOW until all Controller power AC Power Recycle (Recycle “On” P.12 supply voltages are normal. This allows time for other transmit- After Power Failure) ter supplies to reach normal voltages and clear the Type 1 fault When primary AC is restored after a power failure, the transmit- induced “off”...
  • Page 238 DX-25U SUMMARY: When AC power fails while the transmitter is The “Supply Fault” signals also generate a Type 1 Fault induced operating, the current power level, and digital power output “OFF” command, but a five-second delay in the Controller data, are stored in the power level latch (U40) and in the supply fault circuit inhibits this command so it is not latched.

  • Page 239: Introduction

    Section Q LED Board (A32) Introduction appropriate indicator on the ColorStat™ panel will latch RED. For Temperature Induced Lower” condition, the OVER TEMP This section describes the LED Board, and includes circuit LED on the Driver Encoder/Temp Sense Board will latch RED functions and descriptions.

  • Page 240: Type 1 Faults

    Clearing the fault will not reset the status indication; the stretcher and OR gate U70A ensure that a “Type 1 Fault-H” to RESET button on the ColorStat™ panel must be depressed, or a Table Q-1. DX 25U Fault Types TYPE 1 TURNS PA POWER SUPPLY OFF (Manual Restart Required)
  • Page 241 Section Q - LED Board (A32) Figure Q-1 LED Board Block Diagram Rev. R: 11-11-96 888-2297-002 WARNING: Disconnect primary power prior to servicing.

  • Page 242: Type 2 Faults

    DX-25U remote “Reset” control input must be received to reset fault b. VSWR Induced Lower: Refer to SECTION P, Controller. INDICATIONS. The VSWR Self-Test circuit checks the VSWR Fault logic by simulating a VSWR signal from the Output Monitor phase Type 2 Faults detector output.

  • Page 243: Circuit Descriptions

    Section Q - LED Board (A32) Q.4.8.3 Latch Outputs Type 3 Faults lower power and do not turn the PA Power Supply The following description refers to Figure Q-3, “Latched Fault OFF. A fault indication indicates that the power output has been Status Indications, Simplified Diagram.”...
  • Page 244 DX-25U Figure Q-2. Reset Circuit, Simplified Diagram 817 1280 101-A 888-2297-002 Rev. R: 11-11-96 WARNING: Disconnect primary power prior to servicing.

  • Page 245: Reset Circuit

    Section Q - LED Board (A32) Reset Circuit Q.5.1 a. Door Interlock logic: Refer to SECTION P, Controller. The reset circuit is on sheet 1 of the LED Board schematic b. External Interlock logic: Refer to SECTION P, Controller. diagram, 839-7855-184, in the Drawing Package. The circuit c.
  • Page 246 DX-25U of indicator DS22. The LOW NOT-Q output turns off the green section of DS22. The LOW NOT-Q output is inverted by U54-6 to provide an AIR FAULT-H logic signal to the External Inter- face. Inhibit “Air Interlock” Status Indication (Gates U62 Q.5.2.3.4 pins 8 and 11) When the transmitter is first turned ON and the Overdrive Inhibit...
  • Page 247 Section Q - LED Board (A32) Delay output are both LOW, both AND gate inputs are LOW, Normally, the sample is lower than the reference voltage, and and U20-3 is LOW. When the Overdrive Inhibit is released (goes the comparator output goes to -15 VDC. Diode CR3 clamps the HIGH), U20-1 goes HIGH but U20-2 remains LOW for an voltage to the input of Logic Level Down Converter U14-3.

  • Page 248: Type 2 Fault Circuits

    DX-25U Regulator Fault Alert Outputs Q.5.2.7.1 Power Supply OFF may correct the condition, so Type 2 Faults For a description of regulator IC operation and faults which cycle the transmitter OFF, then back ON. cause a “fault alert” refer to SECTION M, “DC Regulator.” Q.5.3.1 Type 2 Fault Action When there is no fault, the “Fault Alert”...
  • Page 249 Section Q - LED Board (A32) tor output is inhibited from registering a fault. After approxi- amplifier input are small; 50 millivolts across the shunt corre- mately 0.3 seconds, the Underdrive “Inhibit” is released. If RF sponds to 100 Amperes of supply current. drive is correct, the RF drive sample voltage will be greater than Peak Current Overload Q.5.3.5.1...

  • Page 250: Type 3 Fault Circuits

    DX-25U Type 3 Fault Circuits on the Controller. For each Fault Logic circuit, the logic HIGH Q.5.4 pulse also goes to the Repeat Fault AND gate. Type 3 Faults LOWER transmitter power but do not turn off the PA Power Supply. A “Type 3 Fault” can be generated by two The logic LOW pulse from the NOT-Q output goes to status conditions: indicator circuits and to the “B”...
  • Page 251 Section Q - LED Board (A32) b. RF DRIVE SWITCH-OVER: NOR gate U3-10 is also a at the NOT-Q output. The one-shots are retriggerable, so that if VSWR Fault - L signal to one-shot U28A which generates another VSWR fault is detected during the 0.5 second pulse a “RF Drive Switch-Over”...
  • Page 252 DX-25U Type 3 Fault Gate: U23-8 Q.5.4.3.4 U38-11 then inverted by U38-3 to provide the VSWR-H output. A Type 3 fault occurs when repeated VSWR “hits” lower A single VSWR “hit” will send a 0.5 second logic HIGH pulse transmitter power. A remote “Type 3 Fault” status indication is to the External Interface, and a latched VSWR output will provided at U23-8 and invertor U8-6.
  • Page 253 Section Q - LED Board (A32) A VSWR condition causes a RED “VSWR Fault” indication by The latch output will then illuminate only the GREEN LED forcing the Q output of the Pulse Stretcher or the Latch HIGH section and there will be NO remote “VSWR Self-Test Indicate” and the output of OR gate U37-11 HIGH.

  • Page 254: Type 4 Fault Circuits

    DX-25U When a VSWR self-test is initiated, U50-11, U26-2, and U8-8 be HIGH when the latch is clocked, and outputs and indication generate a 0.5 millisecond logic LOW pulse at U8-8 output as circuit conditions will be as follows: follows: a.
  • Page 255 Section Q - LED Board (A32) Figure Q-5. VSWR Logic, Simplified Diagram 817 2099 037 Rev. R: 11-11-96 888-2297-002 Q-17 WARNING: Disconnect primary power prior to servicing.

  • Page 256: Type 5 Faults Circuit

    DX-25U alert transistor and J7-11 input will go LOW. A Type 4 Fault will When the “OVERDRIVE INHIBIT-L” signal is present, the be generated by comparator U67-1. output of the gate will be LOW no matter what the “Conversion Error” logic signal state is and the Conversion Error indicator Q.5.5.4 Analog to Digital Converter: +15V Supply will be green.
  • Page 257 Section Q - LED Board (A32) Figure Q-6. VSWR Self-Test Logic, Simplified Diagram 817 1280 106 Rev. R: 11-11-96 888-2297-002 Q-19 WARNING: Disconnect primary power prior to servicing.

  • Page 258: Osc Test Switch S1

    DX-25U Buffer Fault Q.5.8.3.2 MORE positive than the Oscillator DC output voltage. When The Oscillator comparator output is LOW and is inverted to hold the comparator’s non-inverting input is more positive, the com- pins 2 and 6 of U6. A Buffer Fault causes gate U6-3 output to go parator output goes logic HIGH.
  • Page 259 Section Q - LED Board (A32) Figure Q-7. "Regulated Supply Fault" Sensing Circuits 817 1280 107 Rev. R: 11-11-96 888-2297-002 Q-21 WARNING: Disconnect primary power prior to servicing.
  • Page 260 DX-25U Figure Q-8. "RF Sense" Circuits, Simplified Diagram 817 1280 099 Q-22 888-2297-002 Rev. R: 11-11-96 WARNING: Disconnect primary power prior to servicing.
  • Page 261 Section Q - LED Board (A32) Table Q-3 LED Board Controls and Indicators COMPONENT FUNCTION/DESCRIPTION DS12 Indicates RED when a +5 Volt regulator fault occurs; otherwise indicates green. DS14 Indicates RED when a -5 Volt regulator fault occurs; otherwise indicates green. DS17 Indicates RED when a +5 Volt regulator fault occurs;...
  • Page 262 DX-25U Table Q-4. LED Board A32, Test Points See Figure Q-10 COMPONENT FUNCTION/DESCRIPTION Power Supply Protection Circuit, AC Sample. TP10 Power Supply Protection Circuit, detected sample (comparator’s non-inverting input). TP11 Power Supply Protection Circuit, Comparator reference voltage. Underdrive fault circuit, Detected rf drive sample. Overdrive fault circuit, Comparator reference voltage.

  • Page 263: Introduction

    Section R Switch Board/meter Panel (A31) Introduction Both multiplexer U3 and the demultiplexer U8 are addressed via a counter IC U6, which is incremented by each closure of the The switch board provides manual pushbutton control for trans- selection switch. At power up, the address is set to 000, which mitter ON/OFF functions, allowing LOW, MED, and HIGH selects the first multimeter position automatically.

  • Page 264: Maintenance

    R.1.4.1 Minus 15 Volt Power Source be checked on other circuit boards in the non-interlocked IC U14 provides the negative power supply voltage that is needed compartment. The paragraphs on “Principles of Opera- by the various op amps. See sheet 2. tion”...

  • Page 265: General Description

    Section S Driver Encoder/Temp Sense Board (A19) General Description 2. If the air flow is further reduced because of restricted filters or the failure of two of the four cooling fans, the The Driver Encoder/Temp Sense Board is located in the Driver AIR LED on the ColorStat™...
  • Page 266 DX-25U Driver Amplifier modules D5, D9 and D10 can be selected regulate the RF drive level by adjusting the voltage to D8. The D8A and D8B voltage can be monitored on the RF MULTIME- during factory test to be ON or OFF by JP1, JP2 and JP3. Some TER on the inside of the Driver Compartment door.

  • Page 267: Temperature Sensor/Power Foldback

    Section S - Driver Encoder/Temp Sense (A19) Temperature Sensor/Power Foldback When S2 is in the OFF position, the AUTO DRIVER D7 is S.2.2 disabled. This position is used only during factory test of the Refer to Figure S-2 for the following discussion. transmitter.

  • Page 268: Air Flow Detection

    DX-25U fied by U10. A DC offset voltage for U10 is provided by U9. At this point NAND gate U8-9 is held HIGH by U11-13 while U8-10 toggles from HIGH to LOW. Each time U12-12 goes The reference for U9 is obtained from zener diode CR7 and is LOW, output U8-8 will go HIGH.

  • Page 269: Cable Interlock Monitor

    Section S - Driver Encoder/Temp Sense (A19) Ohm, 20W resistor, by an angle bracket. The output of U17-2 Due to the voltage divider action of R25, R26, R27, R28, and is connected to the non-inverting input of differential amplifier R25, R31, R32 (through the interlock circuit), the voltage at U18-3.
  • Page 270  ...

  • Page 271: Introduction

    Appendix A Lightning Protection Recommendation Introduction a.1. hazards than lightning. Some of these sion lines causing large induced voltage What do you do with a 2 million volt pulse anomalies are listed and defined: that destroy high voltage rectifier stacks pushing 220,000 amps of current into your a.

  • Page 272: Ac Service Protection

    • Antenna coupling unit connected to an- tenna ground. • The π circuit is equivalent to the normal Tee used by Harris. • Underground coax. • Guy wire length broken by insulators and grounded at the bottom end. The transmitter building must be given Figure a-2.

  • Page 273: Conclusion

    • MCG Electronics, Inc. of entrance and in addition have a ferrite prevented. Install surge protection on all • EFI Corp. choke around it located between the en- incoming and outgoing lines at the wall of • General Electric trance point and the equipment rack. This the building connected to a well designed will provide a high impedance for current ground system.
  • Page 274 Figure a-6. Basic Elements of a Properly Designed Antenna System Figure a-7. Surge Protectors and Ferrite Choke WARNING: Disconnect primary power prior to servicing.

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