Garmin GTX 327 ATC Maintenance Manual
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Garmin GTX 327 ATC Maintenance Manual

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GTX 327 ATC
TRANSPONDER
MAINTENANCE
MANUAL
â â â â
GARMIN International, Inc.
st
1200 E. 151
Street
Olathe, KS 66062 USA
190-00187-05 Revision B
December 2001
The document reference is online, please check the correspondence between the online documentation and the printed version.

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  • Page 1 GTX 327 ATC TRANSPONDER MAINTENANCE MANUAL â â â â GARMIN International, Inc. 1200 E. 151 Street Olathe, KS 66062 USA 190-00187-05 Revision B December 2001 The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 2 GARMIN Corporation. GARMIN Corporation hereby grants permission to download a single copy of this manual and of any revision to this manual onto a hard drive or other electronic storage...
  • Page 3 Specialized test equipment and extensive depot level repair training are required for testing the equipment covered in this manual. Therefore, this manual may not be used to test or repair the subject equipment unless the using facility has been specifically authorized by GARMIN to do so. GTX 327 MAINTENANCE MANUAL...

  • Page 4: Table Of Contents

    TABLE OF CONTENTS SECTION 1 DESCRIPTION AND OPERATION PARAGRAPH PAGE INTRODUCTION......................1-1 GENERAL DESCRIPTION..................... 1-1 PURPOSE OF EQUIPMENT..................1-2 1.3.1 ATCRBS System Operation ..................1-2 1.3.2 Interrogator....................... 1-3 1.3.3 Transponder ......................1-3 1.3.4 Radar Screen, TCAS Display ................... 1-4 1.3.5 Mutual Suppression Pulses ..................
  • Page 5 SECTION 3 TROUBLESHOOTING TROUBLESHOOTING EQUIPMENT ................3-1 TROUBLESHOOTING THE GTX 327 ................3-1 INITIAL INSPECTION OF UNIT ..................3-2 FUNCTIONAL TEST, STANDARD TEST SETUP AND TEST SIGNAL......3-2 POWER ON CHECK...................... 3-2 MAIN BOARD ASSEMBLY..................... 3-3 DISPLAY ASSEMBLY ....................3-3 RECEIVER AND TRANSMITTER ASSEMBLIES ............
  • Page 6 SECTION 5 TESTING INTRODUCTION......................5-1 GENERAL ........................5-1 ADJUSTMENT/MEASUREMENT ACCURACY .............. 5-1 TEST EQUIPMENT PRECAUTION................5-2 REQUIRED TEST EQUIPMENT ..................5-2 5.5.1 TEST HARNESS ...................... 5-2 BENCH TESTING ......................5-2 TEST EQUIPMENT SETUP ................... 5-2 5.7.1 ATC-1400A and Oscilloscope Default Settings............5-4 STANDARD TEST SIGNALS ..................
  • Page 7 SECTION 6 REPLACEABLE ASSEMBLIES LIST OF REPLACEABLE PARTS .................. 6-1 SECTION 7 ASSEMBLY DRAWINGS ASSEMBLY DRAWINGS ....................7-1 LIST OF FIGURES Figure Page ATCRBS System ......................1-2 Typical TCAS Encounter....................1-3 GTX 327 System Block Diagram .................. 1-5 Blindmate Antenna Connector ..................2-1 DB-25 Pin-Out Definitions .....................
  • Page 8 This page intentionally left blank GTX 327 MAINTENANCE MANUAL Page vi Rev. B 190-00187-05 The document reference is online, please check the correspondence between the online documentation and the printed version.

  • Page 9: Introduction

    GTX 327 Installation Manual, 190-00187-02. This manual is designed to aid the bench technician in isolating failures to the assembly level only. If necessary, the GTX 327 can be returned to GARMIN for all service work, including maintenance and repair. Contact GARMIN at the following address for more details: GARMIN 1200 E.

  • Page 10: Purpose Of Equipment

    PURPOSE OF EQUIPMENT The GARMIN GTX 327 Transponder System provides an air to ground link in the Air Traffic Control Radar Beacon System (ATCRBS) to support in-flight aircraft identification. It also provides air to air link participation in the airborne Traffic Alert and Collision Avoidance System (TCAS) for aircraft equipped with Traffic Avoidance equipment.

  • Page 11: 1.3.2 Interrogator

    Similar to the ground based interrogator, an airborne TCAS processor transmits interrogation signals searching for airborne traffic in relatively close proximity. TCAS is capable of detecting the direction and altitude of an aircraft equipped with a transponder such as the GARMIN GTX 327. Typical TCAS equipment is shown in figure 1-2.

  • Page 12: Radar Screen, Tcas Display

    1.3.4 Radar Screen, TCAS Display The radar screen displays returns from both the primary surveillance radar system and the ATCRBS. The ATC system controllers use these returns, called targets, to identify traffic. Similarly, the TCAS display indicates the presence of airborne traffic showing direction, distance and altitude. 1.3.5 Mutual Suppression Pulses Other equipment on board the aircraft may transmit in the same frequency band as the transponder, such as DME...

  • Page 13: Scope Of Maintenance

    • Front Panel Subassembly Refer to figure 1-3 for a simplified system block diagram. The subassemblies are not field repairable. For a complete list of all GARMIN authorized replaceable parts, see Table 6-1, Field Replaceable Parts List. RECEIVER LCD DISPLAY...

  • Page 14: Main Board Assembly

    1.6.1 Main Board Assembly The Main Board Assembly is the functional center of the unit. The Main Board communicates with all the components of the unit, and provides information to and from the Front Panel for the interface with the pilot. The Main Board contains the following circuits: •...

  • Page 15: Diplexer Coax Cable

    1.6.5 Diplexer Coax Cable The GTX 327 Receiver and Transmitter are connected to a common BNC connector at the rear of the unit through subminiature coax cables and RF connectors. Cable length and placement of this cable is critical to proper operation. The cable assy is used as a diplexer, allowing both the transmitter and receiver to use the same BNC antenna connector.
  • Page 16 This page intentionally left blank GTX 327 MAINTENANCE MANUAL Rev B 190-00187-05 The document reference is online, please check the correspondence between the online documentation and the printed version.

  • Page 17: Special Test Equipment

    This section identifies the special test equipment essential to maintain the GTX 327. Standard equipment is not listed. For any questions regarding warranty repair of the unit contact the GARMIN Customer Service Department at the address or phone number listed in Section 1.

  • Page 18: Test Harness

    1. Trim coax outer insulation back 0.50”. 2. Trim braid (not center conductor or insulation) back 0.25”. 3. Strip Insulation back 0.12”. NOTE Place the ferrule over the coax braid, flush against the coax outer insulation before performing the next step if the outside diameter of the coax braid is smaller than the inside diameter of the center connector sidewall opening.
  • Page 19 Unit Connector As Viewed From Rear Of Unit. DESCRIPTION AVIONICS MASTER ON RS232 IN 2 ALTITUDE A1 ALTITUDE C2 ALTITUDE A2 ALTITUDE A4 ALTITUDE C4 EXTERNAL IDENT INPUT ALTITUDE B1 ALTITUDE C1 ALTITUDE B2 ALTITUDE B4 POWER GROUND SWITCHED POWER OUTPUT POWER INPUT (+11 TO +33 VDC) EXTERNAL STANDBY EXTERNAL SUPPRESSION...
  • Page 20 This page intentionally left blank GTX 327 MAINTENANCE MANUAL Rev B 190-00187-05 The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 21 Figure 2-3. GTX 327 Test Setup/Test Harness GTX 327 MAINTENANCE MANUAL Page 2-5 (Page 2-6 Blank) 190-00187-05 Rev B The document reference is online, please check the correspondence between the online documentation and the printed version.

  • Page 22: Troubleshooting

    SECTION 3 TROUBLESHOOTING The GTX 327 Transponder contains static sensitive components. Observe proper anti-static procedures when testing the unit. WARNING Hazardous voltages exist on the main board and transmitter board. Under normal operating conditions the voltages range up to 60 Vdc. Exercise extreme caution during unit testing.

  • Page 23: Initial Inspection Of Unit

    INITIAL INSPECTION OF UNIT If the initial bench test indicates a problem with the transponder, first remove DC power from the unit and open it to visually inspect for damaged or loose components or evidence of heat stressed components. Visually check each of the flex cables to verify that they are undamaged and fully seated into their connectors.

  • Page 24: Main Board Assembly

    Table 3-1. Main Board Power Supply Voltages and Tolerances COMPONENT VOLTAGE TOLERANCE ±2.0 Vdc Q309 Collector +54.0 Vdc ±0.2 Vdc Q310 Emitter -5.1 Vdc ±0.75 Vdc D308 Cathode +14.45 Vdc ±0.2 Vdc D309 Cathode +5.1 Vdc ±0.25 Vdc D310 Anode -12.0 Vdc ±2.5 Vdc D306 Cathode...
  • Page 25 Table 3-2. Key Matrix Test ACTIVE INPUT COLUMN ASSIGNMENT OUTPUT KEY COL 1 KEY COL 2 KEY COL 3 KEY COL 4 KEY COL 5 (R218) (R219) (R220) (R221) (R222) KEY ROW 1 START/STOP NOT USED (J103-16) KEY ROW 2 NOT USED (J103-17) KEY ROW 3...

  • Page 26: Receiver And Transmitter Assemblies

    If the KEY LED DIMMING fails, verify the following: 7. Q501-4 has a 4 kHz PWM similar to the traces shown in figure 3-1. 8. Verify that as the display dims, the PWM duty cycle decreases. After performing the steps listed, replace the front display assembly if: •...
  • Page 27 Replace the transmitter assembly if, while the unit is receiving valid interrogations, the ATC-1400A indicates no RF output while: 1. No problems are found with the diplexer coax cables and/or connectors. 2. Pulses are present at TP500, TP527 & TP518 on the transmitter board. 3.
  • Page 28 Table 3-3. Test Failures and Recommended Actions TEST FAILURE TEST RECOMMENDED ACTION PARAGRAPH Visual Inspection Replace damaged cables, diplexer, chassis components and board assemblies as required Power On Check 3.5, 5.9.4 If voltage is not measured at fuse F301, replace fuse on main board Switched Power Output 5.10...
  • Page 29 J-3271 F301 Q302 D309 I301 D310 D306 D308 J101 Q310 Q309 Q309 COLLECTOR R222 COL. 5 R221 COL. 4 I-204 R220 COL. 3 R219 COL. 2 R213 COL. 1 J102 D507 Q501 D506 D508 J103 D509 Note: Dot denotes pin 3 on D506-D509 Figure 3-2.
  • Page 30 TP500 TP527 TP518 P501 SIGNAL -5 Vdc TX OSC ON TX EMITTER ON TX FINAL ON +53 Vdc Figure 3-3. Transmitter Board Component Layout GTX 327 MAINTENANCE MANUAL Page 3-9 190-00187-05 Rev. B The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 31 P301 +11.9 to +14 Vdc VOLTAGE +12 Vdc -12 Vdc 11,12 +14.5 Vdc Figure 3-4. Receiver Board Component Layout 3-10 GTX 327 MAINTENANCE MANUAL Rev B 190-00187-05 The document reference is online, please check the correspondence between the online documentation and the printed version.

  • Page 32: Disassembly And Reassembly

    SECTION 4 DISASSEMBLY AND REASSEMBLY INTRODUCTION This section contains the instructions for removing the major assemblies of the GTX 327 Transponder. Reassembly instructions are given in paragraph 4.4. Disassemble the unit only to the extent necessary to remove and replace parts or assemblies affected. Replaceable parts and assemblies are listed in Section 6, REPLACEABLE ASSEMBLIES.

  • Page 33: Removing The Bottom Cover

    4.3.1 Removing the Bottom Cover (Figure 7-2) 1. Remove six screws securing the bottom cover assembly (20) to the unit, four from the sides (15) and two black screws (14) through the bottom of the front panel (1). 2. Slide the bottom cover towards the rear until the retaining lip is fully exposed, then lift the cover assembly off of the unit.

  • Page 34: Display Assembly

    4.3.4 Display Assembly (Figure 7-1) 1. Remove the front panel assembly (1) as described in paragraph 4.3.3. 2. Remove two screws (12) securing the display module (3) to the front panel assembly (1). 3. Carefully lift the display assembly off of the PCB connector, and then pull the display assembly sideways away from the retaining tabs on the front panel.

  • Page 35: Main Board

    4.3.7 Main Board (Figure 7-3) 1. Disconnect the multipin ribbon cable (10) if not already removed with the transmitter board in step 4.3.6. 2. Carefully pull up on the retaining lip of the ZIF connector with a right-angle tool. 3. Gently pull the flexible ZIF circuit cable (21) from the connectors. 4.

  • Page 36: Reassembly

    REASSEMBLY 4.4.1 Coaxial Cable Diplexer Assembly (Figures 7-2, 7-3) CAUTION If the coaxial cable assembly is damaged, do not attempt repairs. Cable length and placement is critical to proper operation. If a break occurs do not trim and resolder this cable. The subminiature RF coax connectors are easily damaged. If the connectors are damaged, or a break occurs, replace the assembly.

  • Page 37: Transmitter Board

    CAUTION Orientation of the blue strain relief band on the cable (21) is important in the next step. When inserted into the main board connector the blue band must face the connector’s brown retaining lip. 5. Carefully insert the ribbon cable (21) into the ZIF connector. 6.

  • Page 38: Display Assembly

    4.4.5 Display Assembly (Figure 7-1) 1. Carefully place the clean lens (2) on the bezel assembly (1) with the stepped edge seated securely in the bezel and the black frame facing rearward. 2. Place the display assembly (3) into the retaining tabs on the bezel assembly and carefully insert the display assembly connector over the bezel assembly pins.

  • Page 39: Installing Bottom Cover

    The 3/4 inch access cover circles (18) and hydrophobic patch (19) need not be removed for normal field maintenance. If these items need to be replaced, order from GARMIN using the part numbers found in table 6-1. GTX 327 MAINTENANCE MANUAL...

  • Page 40: Introduction

    SECTION 5 TESTING INTRODUCTION The test procedures in this section are provided to aid the technician in locating faulty assemblies within the unit. The test procedures can be performed before troubleshooting is started or they can be used as a “return to service”...

  • Page 41: Test Equipment Precaution

    TEST EQUIPMENT PRECAUTION Except for the DVM with standard lead length, the case of each instrument should be connected to ground. The bench power supply ground must be connected to earth ground and serve as a single point ground for the entire test setup.
  • Page 42 Figure 5-1. ATC-1400A Test Set GTX 327 MAINTENANCE MANUAL Page 5-3 190-00187-05 Rev. B The document reference is online, please check the correspondence between the online documentation and the printed version.

  • Page 43: Atc-1400A And Oscilloscope Default Settings

    5.7.1 ATC-1400A and Oscilloscope Default Settings Configure the ATC-1400A switches as shown in Figure 3-1. • Set RF Level to –50 dBm • Set XPDR MODE switch to position A • Set PRF to 500 Hz • Turn SLS to OFF Set the Oscilloscope to the following initial settings: •...

  • Page 44: Panel Lighting

    NOTE For units installed in a particular aircraft, you need check only the lighting voltage appropriate to that aircraft. 5.9.1 28 V Panel Lighting 1. Set panel lighting input voltage to +27.5 V and apply the voltage to the transponder test harness, pin 2.

  • Page 45: Display Dimming Test

    5.9.5 Display Dimming Test 1. Cover the ambient light sensor located next to the 7 key. 2. Observe that the display dims when the sensor is covered. 5.10 SWITCHED POWER OUTPUT Switched power output can be tested by supplying power to an encoding altimeter from the test harness, pin 14. Make sure that the current draw does not exceed 1.5 amps at +13.75 Vdc.

  • Page 46: Timer Function Test

    • START/ STOP  Starts and stops the Count Up and Count Down timers. • CRSR  Activates the change fields for the Count Down timer when selected by the FUNC key. • CLR  Resets the Count Up and Count Down timers. •...

  • Page 47: Receiver Test, Minimum Trigger Level And Dynamic Range

    5.12.1 Receiver Test, Minimum Trigger Level and Dynamic Range Configure the ATC-1400A switches as shown in Figure 3-1. • Set RF Level to –50 dBm • Set XPDR MODE switch to position A • Set PRF to 500 Hz • Turn SLS to OFF Minimum Triggering Level (MTL) is defined as the RF input level of a standard test signal that produces 90% reply.
  • Page 48 Pulse Width Measure the pulse width of the detected pulse P1. The pulse width measured at the 50% point must be between 350 ns and 550 ns. Pulse Rise Time Measure the rise time of the detected pulse P1. The rise time measured from the 10% to 90% points must be between 50 ns and 100 ns.

  • Page 49: Reply Rate Limiting Test

    Figure 5-2. Transmitter Shield Cover Alignment Cutouts 5.12.4 Reply Rate Limiting Test 1. Set the PRF switches to 1200 Hz and verify that the percent reply is at or between 97 and 100%. 2. Set the PRF switches to 1800 Hz and verify that the percent reply is not greater than 70%. 3.

  • Page 50: Ident Test

    5.12.6 IDENT Test 1. Set the ATC-1400A to Mode A and place the GTX 327 in ON mode. 2. Adjust the RF level of the ATC-1400A for a 100% reply rate. 3. Press the IDENT button on the transponder. 4. The ATC-1400A XPDR Code display shall read 1d0000 for approximately 20 seconds. The SPI pulse shall appear next to the F2 pulse on the oscilloscope.
  • Page 51 This page intentionally left blank 5-12 GTX 327 MAINTENANCE MANUAL Rev B 190-00187-05 The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 52 The following GTX 327 Transponder assemblies can be field replaced. The table below lists the part numbers available to authorized maintenance shops: Table 6-1. Field Replaceable Parts List, 1 of 2. Item Assembly Garmin Part Numbers Front Panel Assembly S11-00491-01 Lens 470-00034-00...
  • Page 53 Table 6-1. Field Replaceable Parts List, 2 of 2. Item Assembly Garmin Part Numbers Fuse, F301, SMT, Fast Blow, 3A 350-B0300-01 Receiver Tray Shield 115-00299-00 Page 6-2 GTX 327 MAINTENANCE MANUAL Rev. B 190-00187-05 The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 54 SECTION 7 ASSEMBLY DRAWINGS ASSEMBLY DRAWINGS The following assembly drawings are provided for part identification and to aid in assembly/disassembly of the GTX 327 Transponder. Figure 7-1. GTX 327 Front Panel Assembly GTX 327 MAINTENANCE MANUAL Page 7-1 190-00187-05 Rev. B The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 55 This page intentionally left blank GTX 327 MAINTENANCE MANUAL Rev B 190-00187-05 The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 56 Figure 7-2. GTX 327 Chassis Assembly, Exploded View GTX 327 MAINTENANCE MANUAL Page (Page 7-4 Blank) 190-00187-05 Rev B The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 57 Figure 7-3. GTX 327 Chassis Assembly, Main Board and Transmitter Board GTX 327 MAINTENANCE MANUAL Page 7-5 (Page 7-6 Blank) 190-00187-05 Rev B The document reference is online, please check the correspondence between the online documentation and the printed version.
  • Page 58 The document reference is online, please check the correspondence between the online documentation and the printed version.

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