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Garmin GTX 327 ATC, Maintenance Manual

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Garmin GTX 327 ATC Maintenance Manual Download Page 45

5-6

GTX 327 MAINTENANCE MANUAL

Rev B

190-00187-05

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.  At input voltages greater than +13.75
Vdc, the power supplied through the switched power output must not exceed the above rating.

Measuring voltage across a resistive load can also test switched power output.  Verify that current does not
exceed 1.5 amps at +13.75 Vdc or its equivalent power rating.

5.11

FRONT PANEL PUSHBUTTON CONTROLS

Exercise all front panel pushbutton controls to verify proper selection and deselection of each LED and
appropriate indication on the GTX 327 front panel display.  The purpose of each function selection switch is as
follows:

•

  OFF 

 Turns the GTX 327 off.

•

  STBY 

Selects STBY mode.

•

  ON 

 Turns the transponder ON in Mode A.

•

  ALT 

 Turns the transponder on in Mode A and Mode C.

•

  IDENT 

 Activates the Special Position Identification (SPI) Pulse.

•

  VFR 

 Selects the default VFR code.

•

  FUNC 

 Changes modes displayed on the right side of the display.  Displayed data includes Flight

Level, Flight Time, Count Up timer, Count Down timer, screen Contrast, and Display
Brightness (if configured for manual contrast and brightness).

Flight Level:

Displays the pressure altitude data supplied to the GTX 327 in feet,
flight level format or meters depending on configuration setup.

Flight Time:

Displays the flight time controlled by the Start/Stop button.  If
AIRBORNE SOURCE is configured the timer begins when liftoff from a
squat switch or when 35 knots from a GPS is sensed.

Count Up Timer:

Controlled by START/STOP and CLR button.

Count Down Timer:

Controlled by START/STOP, CLR, and CRSR buttons.  Count down
timer entered with 0 – 9 buttons.

Contrast:

Controlled by 8 and 9 buttons.

Display Brightness:

Controlled by 8 and 9 buttons.

The document reference is online, please check the correspondence between the online documentation and the printed version.

Summary of Contents for GTX 327 ATC

Page 1: ... E 151st Street Olathe KS 66062 USA 190 00187 05 Revision B December 2001 GTX 327 ATC TRANSPONDER MAINTENANCE MANUAL The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 2: ... is strictly prohibited GARMIN International Inc 1200 E 151 st Street Olathe KS 66062 USA Telephone 913 397 8200 Dealer Line 1 800 800 1420 Website Address www garmin com INFORMATION SUBJECT TO EXPORT CONTROL LAWS This document may contain information which is subject to the Export Administration Regulations EAR issued by the United States Department of Commerce 15 CFR Chapter VII Subchapter C and...

Page 3: ...ard Components that retain a charge shall be discharged only when such grounding does not result in equipment damage If a test connection to energized equipment is required make the test equipment ground connection before probing the voltage or signal to be tested DO NOT SERVICE ALONE Personnel shall not under any circumstances reach into or enter any enclosure for the purpose of servicing or adju...

Page 4: ... TECHNICAL SPECIFICATIONS 1 4 1 5 SCOPE OF MAINTENANCE 1 5 1 6 EQUIPMENT DESCRIPTION 1 5 1 6 1 Main Board Assembly 1 6 1 6 2 Front Panel 1 6 1 6 3 Transmitter 1 6 1 6 4 Receiver 1 6 1 6 5 Diplexer Coax Cable 1 7 1 6 6 Flexible Circuit Cables 1 7 SECTION 2 SPECIAL TEST EQUIPMENT 2 1 INTRODUCTION 2 1 2 2 SPECIAL TOOLS AND TEST EQUIPMENT 2 1 2 2 1 Antenna Test Cable Connector 2 1 2 2 2 Test Harness 2...

Page 5: ...EMBLING THE UNIT 4 1 4 3 1 Removing the Bottom Cover 4 2 4 3 2 Flexible Circuit Cables 4 2 4 3 3 Front Panel Assembly 4 2 4 3 4 Display Assembly 4 3 4 3 5 Receiver Module Assembly 4 3 4 3 6 Transmitter Board 4 3 4 3 7 Main Board 4 4 4 3 8 Coaxial Cable Diplexer Assy 4 4 4 4 REASSEMBLY 4 5 4 4 1 Coaxial Cable Diplexer Assy 4 5 4 4 2 Main Board 4 5 4 4 3 Transmitter Board 4 6 4 4 4 Receiver Module A...

Page 6: ...l Lighting 5 5 5 9 3 5 V Panel Lighting 5 5 5 9 4 Power On Test 5 5 5 9 5 Display Dimming Test 5 6 5 10 SWITCHED POWER OUTPUT 5 6 5 11 FRONT PANEL PUSHBUTTON CONTROLS 5 6 5 11 1 Timer Function Test 5 7 5 11 2 Code Selector Pushbutton Switches 5 7 5 11 3 Configuration Pages 5 7 5 12 FUNCTIONAL TEST 5 7 5 12 1 Receiver Test Minimum Trigger Level and Dynamic Range 5 8 5 12 2 Transmitter Power Output ...

Page 7: ... 327 Test Setup Test Harness 2 5 3 1 4 kHz PWM Signal on Q501 3 4 3 2 Main Board Component Layout 3 8 3 3 Transmitter Board Component Layout 3 9 3 4 Receiver Board Component Layout 3 10 4 1 Diplexer Cable Orientation 4 5 5 1 ATC 1400A Test Set 5 3 5 2 Transmitter Shield Cover Alignment Cutouts 5 10 7 1 GTX 327 Front Panel Assembly 7 1 7 2 GTX 327 Chassis Assembly Exploded View 7 3 7 3 GTX 327 Chas...

Page 8: ...327 MAINTENANCE MANUAL Rev B 190 00187 05 Page vi This page intentionally left blank The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 9: ...functions The transponder is a radio transmitter and receiver that operates on radar frequencies receiving ground radar interrogations at 1030 MHz and transmitting a coded response of pulses to ground based radar on a frequency of 1090 MHz As with other Mode A Mode C transponders the GTX 327 replies with any one of 4 096 codes which differ in the position and number of pulses transmitted By replyi...

Page 10: ...he GTX 327 to reply with identification information useful to ATC Special codes may be selected to indicate conditions such as emergency or VFR traffic In addition to Mode A operation for identification Mode C is available for altitude information when an altitude encoder is connected to the GTX 327 and altitude replies are selected 1 3 1 ATCRBS System Operation There are two classes of radar syst...

Page 11: ...orne 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 Figure 1 2 Typical TCAS Encounter 1 3 3 Transponder When the interrogation signal is detected by the GTX 327 an app...

Page 12: ...ansponder This feature is designed to limit mutual interference 1 4 TECHNICAL SPECIFICATIONS Refer to the GTX 327 Installation Manual for a complete list of specifications SPECIFICATION CHARACTERISTIC TSO JTSO TSO C74c Class 1A JTSO C74c Class 1A RTCA DO 160D Refer to GTX 327 Installation and Operation Manual 190 00187 02 Appendix A Power Requirements 11 0 to 33 0 Vdc Power Input 15 Watts typical ...

Page 13: ...ur major electrical assemblies Main Board Assembly Receiver Board Transmitter Board 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 DIPLEXER MAIN BOARD LCD DISPLAY AND KEYBOARD TRANSMITTER MODULATOR RECEIVER Figure 1 ...

Page 14: ...g and transponder functions and enters the selected code SPI and timing commands The Front Panel contains the following circuits LCD Display with LED backlighting Mode Selection Keys Pushbutton Data Entry Keys Ambient Light Sensor 1 6 3 Transmitter The Transmitter transmits the coded pulses The Transmitter contains the following circuits Pulse Modulator Ceramic Resonator with Pulse Power Oscillato...

Page 15: ...0 MHz At 1090 MHz the coax cable going to the receiver appears as an open circuit while at 1030 MHz the coax cable going to the transmitter appears as an open circuit The routing of the coax cables inside the unit is critical as well Note how the cables are routed before removing Make sure the cables are replaced in the same location as originally installed 1 6 6 Flexible Circuit Cables The major ...

Page 16: ...8 GTX 327 MAINTENANCE MANUAL Rev B 190 00187 05 This page intentionally left blank The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 17: ... Fabricated Test Harness Locally Fabricated See figure 2 3 Coaxial Adapter Female BNC to male type N 2 2 1 Antenna Test Cable Connector The antenna test cable requires a BNC connector at the test fixture antenna and a male BNC Blindmate connector GARMIN P N 330 00198 00 or RF Adapter P N 330 00326 00 at the GTX 327 Transponder Instructions for installing the Blindmate BNC are shown in steps 1 thro...

Page 18: ...ply solder between the braid and the sleeve Continue to apply heat until the solder flows evenly 6 Install 50 8 Matching Bushing 7 Insert connector cap and tack solder in two places 2 2 2 Test Harness A test harness must be fabricated locally to connect the GTX 327 to the ATC 1400A Transponder Test Set All electrical connections except for the antenna are made through a single 25 pin D connector F...

Page 19: ...11 ALTITUDE B2 In 12 ALTITUDE B4 In 13 POWER GROUND In 14 SWITCHED POWER OUTPUT Out 15 POWER INPUT 11 TO 33 VDC In 16 EXTERNAL STANDBY In 17 EXTERNAL SUPPRESSION In Out 18 ALTITUDE D4 In 19 RS232 IN 1 In 20 RS232 OUT 1 Out 21 RESERVED 22 SQUAT SWITCH In 23 28 VDC PANEL LIGHTING INPUT In 24 14 VDC 5 VDC PANEL LIGHTING INPUT In 25 POWER GROUND In Figure 2 2 DB 25 Pin Out Definitions The document ref...

Page 20: ...4 GTX 327 MAINTENANCE MANUAL Rev B 190 00187 05 This page intentionally left blank The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 21: ...NCE MANUAL Page 2 5 Page 2 6 Blank 190 00187 05 Rev B Figure 2 3 GTX 327 Test Setup Test Harness The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 22: ...ation in this section as an aid in troubleshooting the GTX 327 Transponder to the replaceable assembly level Proceed with troubleshooting using the following procedures circuit board diagrams found at the end of this section and Table 3 3 Testing Failures and Recommended Actions In general entry into the troubleshooting section occurs after a failure in the testing section After the faulty module ...

Page 23: ...in an aircraft adjust the power input to the unit under test to the aircraft voltage must be between 11 Vdc and 33 Vdc Apply the appropriate Light Dimming voltage as used in the aircraft installation Refer to Figure 2 3 for test setup Configure the oscilloscope to monitor both the ATC 1400A interrogation pulses GEN and the GTX 327 detected transmitter pulses XMTR 3 5 POWER ON CHECK If the unit fai...

Page 24: ...trix test to isolate problems to either the front display assembly or main board assembly The key matrix test Table 3 2 states the points to check for testing the front panel keys The column and row points are identified on the main board diagram Figure 3 2 With no front panel buttons depressed key columns are normally pulled high to 5 volts Key rows are low but are sequentially strobed high by th...

Page 25: ...302 3 go LOW when the ON key is pressed 2 D509 3 and Q302 3 go LOW when the STBY key is pressed 3 D508 3 and Q302 3 go LOW when the ALT key is pressed If the OFF KEY fails verify the following 4 D506 3 goes LOW when the OFF key is pressed Approximately 2 seconds later Q302 1 goes LOW If the DISPLAY DIMMING fails verify the following 5 Verify the signal on Q501 4 has a 4 kHz pulse width modulation ...

Page 26: ...here are pulses lift and rotate the receiver over to access the transmitter Referring to the P501 signal levels in Figure 3 2 verify that all power supply voltages are correct in the transmitter Verify that the modulation pulses just checked on the main board are also seen at TP500 TP527 and TP518 on the transmitter These pulses drive the modulator and enable the transmitter If these pulses are co...

Page 27: ...plexer coax cables and or connectors 2 Pulses are present at TP500 TP527 TP518 on the transmitter board 3 All transmitter receiver and main board power supply voltages are correct 4 No problems are found with the flex cables 5 Front panel LCD indicates that unit is replying to interrogations The document reference is online please check the correspondence between the online documentation and the p...

Page 28: ...d altitude inputs at J3271 but no altitude pulses transmitted 3 6 5 12 1 Replace Main Board see paragraphs 4 3 7 4 4 2 FRONT DISPLAY TESTS Error found in matrix test Table 3 2 or steps listed in paragraph 3 7 3 7 Replace Front Display Assembly see paragraphs 4 3 4 4 4 5 Keyboard test locates a fault not related to main board assembly 3 7 Replace Front Display Assembly see paragraphs 4 3 4 4 4 5 RE...

Page 29: ...D507 D506 D508 D509 Q501 Note Dot denotes pin 3 on D506 D509 D309 D306 1 2 2 1 J102 J101 Figure 3 2 Main Board Component Layout R222 COL 5 R221 COL 4 R220 COL 3 R219 COL 2 R213 COL 1 Q309 COLLECTOR D308 Q310 Q302 The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 30: ...gure 3 3 Transmitter Board Component Layout TP500 TP527 TP518 P501 PIN SIGNAL 1 5 Vdc 2 TX OSC ON 4 TX EMITTER ON 5 TX FINAL ON 9 53 Vdc The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 31: ...0 00187 05 Figure 3 4 Receiver Board Component Layout P301 PIN VOLTAGE 5 12 Vdc 11 12 14 5 Vdc 11 9 to 14 Vdc 12 Vdc TP2 The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 32: ...ace assemblies with the unit turned on To avoid damaging the circuit boards and assemblies the following procedures should be carefully followed 4 2 REQUIRED TOOLS Standard shop equipment is used to remove and replace faulty assemblies NOTE The GTX 327 lens is coated with a special anti reflective coating which is very sensitive to skin oils waxes and abrasive cleaners It is very important to clea...

Page 33: ...m cover assembly 20 as described in paragraph 4 3 1 2 Carefully pull up on the retaining lip of the ZIF connector with a right angle tool similar to a dental pick The retaining lip will break if pulled too hard 3 Gently pull the flexible circuit cable from the connector 4 3 3 Front Panel Assembly Figures 7 1 7 2 NOTE To avoid damaging the unit remove flexible circuit cables connecting the front pa...

Page 34: ...the receiver tray shield 23 off of the receiver 3 Carefully pull up on the retaining lip of the ZIF connector with a right angle tool 4 Gently pull the flexible ZIF circuit cable 21 from the connector 5 Carefully lift the coaxial cable connector P O item 8 from the board 6 Remove two screws 13 in opposite corners securing the receiver module 6 to the chassis 17 7 Lift the receiver module off of th...

Page 35: ...sily damaged If the connectors are damaged or a break occurs replace the assembly The GTX 327 internal coax cable assembly 8 is critical The cable assembly is used as a diplexer allowing both the transmitter and receiver to use the same BNC antenna connector A fixture is necessary to ensure that the lengths are very precisely measured and assembled Also the routing of the coax cables is critical a...

Page 36: ...ble orientation 2 Secure the coaxial cable assembly to the chassis with two screws 12 3 Carefully attach the subminiature RF coax connectors to the transmitter board in the steps indicated in paragraph 4 4 3 and to the receiver board in paragraph 4 4 4 4 Place the receiver diplexer cable under the receiver cover retaining clips To avoid exceeding the minimum bend radius of the cable install as sho...

Page 37: ...oard with eight screws 12 4 Connect the multipin ribbon cable connector 10 5 Observing the caution in step 4 4 1 carefully insert the coaxial cable subminiature RF coax plug P O item 8 into the connector on the board 4 4 4 Receiver Module Assembly Figure 7 2 1 Place the receiver module 6 into the chassis 17 2 Attach the receiver module to the unit chassis with two screws 13 in opposite corners 3 C...

Page 38: ...op holes in the bezel 3 Install the flexible circuit cable 9 as described in paragraph 4 4 7 4 4 7 Flexible Circuit Cables Figure 7 3 CAUTION Orientation of the blue strain relief band on the cable is important When inserted into the connectors the blue bands must face toward the brown retaining lip of the connector 1 With the retaining lip of the ZIF connectors lifted carefully insert the flexibl...

Page 39: ... Secure the bottom cover with four screws 15 through the sides and two black screws through the front panel assembly 14 NOTE 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 The document reference is online please check the correspondence betw...

Page 40: ... are the test equipment required test setup data and testing procedures for units removed from an aircraft or from storage before use in an aircraft Perform these tests with the dust covers on After failure of a specific test the unit may be returned to the factory for repair or opened for further testing and troubleshooting Repair is limited to replacement of field replaceable assemblies listed i...

Page 41: ...ness Fabricated Locally See Section 2 Coax Cable Assembly Fabricated Locally See Section 2 5 5 1 TEST HARNESS Section 2 SPECIAL TEST EQUIPMENT provides a schematic diagram in Figure 2 3 for fabricating a suggested test harness Instructions are also given in Figure 2 1 for assembling the blindmate connector on the Coax Cable Assembly The Coax Cable Assembly is included as part of the test harness s...

Page 42: ...X 327 MAINTENANCE MANUAL Page 5 3 190 00187 05 Rev B Figure 5 1 ATC 1400A Test Set The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 43: ...input test signal shall be 1090 MHz at 50 dBm with the PRF set to 500 Hz The XPDR mode switch on the ATC 1400A must be either in mode A or C Set the ATC 1400A RF Level to 50 dBm except for tests necessary to measure MTL Dynamic Range or SLS performance 5 9 POWER ON CHECK Adjust the power supply voltages before connecting the unit Verify that the GTX 327 has been correctly configured for the Panel ...

Page 44: ...e from 13 75 V to 0 V 3 Observe that the panel lights continuously dim while reducing the lighting buss voltage 5 9 3 5 V Panel Lighting 1 Set panel lighting input voltage to 5 V and apply the voltage to the transponder test harness pin 24 2 Vary the panel lighting input voltage from 5 V to 0 V 3 Observe that the panel lights continuously dim while reducing the lighting buss voltage 5 9 4 Power On...

Page 45: ...ns the GTX 327 off STBY Selects STBY mode ON Turns the transponder ON in Mode A ALT Turns the transponder on in Mode A and Mode C IDENT Activates the Special Position Identification SPI Pulse VFR Selects the default VFR code FUNC Changes modes displayed on the right side of the display Displayed data includes Flight Level Flight Time Count Up timer Count Down timer screen Contrast and Display Brig...

Page 46: ...splay When checking the EXTERNAL SWITCH Page verify the appropriate test harness switch operation 5 11 3 Configuration Pages Holding down the FUNC key and pressing the ON key provides access to the configuration pages The FUNC key will sequence through the configuration pages The CRSR key will highlight selectable fields on each page When a field is highlighted numeric data entry will be performed...

Page 47: ...ng with input signal levels at MTL and above the XMTR PWR display on the ATC 1400A shall read greater than 125 watts through the calibrated 1 5 dB coax cable 2 Verify that the front panel display REPLY annunciator is active while the ATC 1400A shows the unit replying 3 Set the ATC 1400A RF level to 90 dBm and verify that the unit does not reply 4 Verify that the front panel display REPLY annunciat...

Page 48: ...ere is no more than 1 dB difference between measured peak power levels Transmitter RF Peak Power Output Verify that RF peak power output is always greater than 125 watts through the calibrated 1 5 dB coax cable to the ATC 1400A Typical RF peak power output through the 1 5 dB coax is 150 watts which correlates to 212 watts peak at the rear of the unit Reply Transmission Frequency Verify that the XM...

Page 49: ...cent reply indicates 90 MTL 2 Adjust the RF level to MTL 3 dB and verify that the unit is replying greater than 90 3 Set the SLS Echo switch to 9 dB and turn the associated toggle switch to ON Verify that percent reply is unchanged from above 4 Set the SLS Echo switch to 0 dB and verify that percent reply is less than 2 5 Adjust the RF level to MTL 25 dB and verify that percent reply is less than ...

Page 50: ...isplay shall read 1d0000 for approximately 20 seconds The SPI pulse shall appear next to the F2 pulse on the oscilloscope The ID annunciator shall indicate on the GTX 327 screen 5 Press the STBY button on the GTX 327 Press the IDENT button on the transponder 6 The ID annunciator shall indicate on the GTX 327 screen but the unit shall not transmit The document reference is online please check the c...

Page 51: ...2 GTX 327 MAINTENANCE MANUAL Rev B 190 00187 05 This page intentionally left blank The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 52: ...e 011 00494 00 7 SMP Transmitter Pocket Shield 115 00298 00 8 Coax Cable Assembly 325 00050 02 9 Flat Flex Cable 310 00019 00 10 Ribbon Cable Assembly 325 00063 00 11 Thermal Pad Transmitter Board 250 00067 00 12 Screw SS 2 56 x 250 211 60232 08 13 Screw SS 2 56 x 500 211 60232 12 14 Screw 4 40 x 187 Black 211 60334 06 15 Screw 4 40 x 250 CSK 211 63234 08 16 Screw 4 40 x 375 CSK 211 63234 10 17 GT...

Page 53: ...eld Replaceable Parts List 2 of 2 Item Assembly Garmin Part Numbers 22 Fuse F301 SMT Fast Blow 3A 350 B0300 01 23 Receiver Tray Shield 115 00299 00 The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 54: ...AWINGS 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 The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 55: ...2 GTX 327 MAINTENANCE MANUAL Rev B 190 00187 05 This page intentionally left blank The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 56: ...ev B 1 20 6 7 17 8 12 14 4x 15 4x 13 2x TO MAIN BD ITEM 4 TO TX BD ITEM 5 TO RX BD ITEM 6 21 23 Figure 7 2 GTX 327 Chassis Assembly Exploded View The document reference is online please check the correspondence between the online documentation and the printed version ...

Page 57: ...0 00187 05 Rev B 4 5 17 9 10 11 16 14 12 14x TO ITEM 3 18 2x 19 Figure 7 3 GTX 327 Chassis Assembly Main Board and Transmitter Board 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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