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3.2.4 Main Board Sub-Assembly Removal

The Main Board Sub-Assembly consists of the Main Board (012-00089-00) and the RF/IF Assembly
(012-00091-00). If required, this sub-assembly may be further dismantled by following the steps in
Section 3.2.5.

1. Remove the covers as described in Section 3.1.

2. Remove the Control/Display Unit as described in Section 3.2.1.

3. Remove the Altitude Decoder Board as described in Section 3.2.2.

4. Remove the hex nut securing the BNC connector to the chassis. This nut is 9/16” and may be removed with a

deep 12-point socket.

5. Pull the BNC connector out of its cutout on the chassis.

6. Remove the heat sink clamping bar (115-00049-00, see Figure 12 - Detail A) by removing the M3 x 5mm mounting

screw (211-50227-05).

7. Remove the heat sink insulator (250-00016-00) from regulator I800 (see Figure 12 - Detail A) and save this piece

for later reassembly.

8. Carefully turn the unit over.

9. The power/dimmer switch uses a flexible circuit cable for connection to the Main Board. This flexible circuit

cable is inserted into a ZIF connector (J804). Pull up on the retaining lip of the ZIF connector. Gently pull the
flexible circuit cable out of the ZIF connector. Take care not to crease the flexible circuit cable.

10. Remove the two #4-40 standoffs (211-63204-08) which hold the 37-pin DSUB connector to the chassis.

11. Remove the M3 x 5mm screw (211-50227-05) and the M3 x 10mm screw (211-50227-15) holding the Main Board to

the chassis.

12. Carefully slide the Main Board upward; pulling it away from the power/dimmer switch and the Interface Board

Connector (J702).

3.2.5 RF/IF Assembly (012-00091-00) Removal

1. Remove the covers as described in Section 3.1.

2. Remove the Altitude Decoder Board as described in Section 3.2.2.

3. Remove the hex nut securing the BNC connector to the chassis. This nut is 9/16” and may be removed with a

deep 12-point socket.

4. Pull the BNC connector out of its cutout on the chassis.

5. Remove the four screws (211-50202-15) and spacers (233-00012-00) which secure the RF/IF Assembly to the

Main Board.

6. Carefully pull the RF/IF Assembly upward, disengaging it from the Main Board Connector (J803). (NOTE: With the

mounting screws removed, the cover for the RF/IF Assembly will be loose. Grip the RF/IF Assembly firmly by the
sides, instead of by its cover, when lifting upward.)

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Summary of Contents for GPS 155

Page 1: ...GPS 155 MAINTENANCE AND REPAIR MANUAL GARMIN INTERNATIONAL PART NUMBER 190 00065 05 1200 E 151st Street REVISION E MARCH 26 1998 OLATHE KANSAS 66062 ...

Page 2: ...ternal Clock Check 8 2 4 TROUBLESHOOTING CHART 9 SECTION 3 DISASSEMBLY INSTRUCTIONS 3 1 REMOVAL OF THE COVERS page 11 3 2 BOARD AND MODULE DISASSEMBLY 12 3 2 1 Control Display Unit Removal 12 3 2 2 Altitude Decoder Board Removal 12 3 2 3 Interface Board Removal 12 3 2 4 Main Board Sub Assembly Removal 13 3 2 5 RF IF Assembly Removal 13 3 2 6 Battery Pack Removal 14 3 2 7 Power Dimmer Switch Remova...

Page 3: ...RAM 5 FIGURE 5 MAIN BOARD TESTPOINTS TOP VIEW 8 FIGURE 6 MAIN BOARD TESTPOINTS BOTTOM VIEW 9 FIGURE 7 RF IF ASSEMBLY REMOVAL 14 FIGURE 8 ROM TOOL INSERTION 17 FIGURE 9 ROM REMOVAL 18 FIGURE 10 J2 REAR CONNECTOR PINOUT DEFINITION 27 FIGURE 11 J101 REAR CONNECTOR PINOUT DEFINITION 28 FIGURE 12 GPS 155 ASSEMBLY DRAWING View 1 30 FIGURE 13 GPS 155 ASSEMBLY DRAWING View 2 31 FIGURE 14 GPS 155 ASSEMBLY ...

Page 4: ...y size and power requirements surface mount components are used extensively Specialized equipment and procedures are required to repair circuit boards having sur face mounted components GARMIN does not authorize the repair of GPS 155 circuit boards All circuit boards and assemblies for the GPS 155 can be economically replaced if necessary The following modules and printed circuit board assemblies ...

Page 5: ... Unit is an assembly consisting of ten keycaps keypad board light pipes optical lens front insert panel vacuum fluorescent display VFD and board with drivers display board shock mounting grommets and screws housed in a die cast bezel with a dual concentric rotary switch and two knobs The VFD is a 3 row by 20 column unit with variable intensity This display provides excellent day and night visibili...

Page 6: ... chip ROM and random access mem ory chips RAM Data stored in RAM is maintained by a 3 volt lithium battery when the unit is switched off and by the regulated 5 volt supply when the unit is powered on A custom LSI is used to decode the signals from the GPS satellites A real time clock IC is used to keep track of the date and time Other circuits on the board are used for input output functions such ...

Page 7: ... AC adapter through a DC power jack located near the rear connector Both of these sources as well as the battery input are diode isolated to prevent parallel sourcing The unit is turned on and off by a digital latch circuit operated by a knob located on the front panel adjacent to the NavData card opening The switching circuit is a fly back design The switching regulator operates at a frequency of...

Page 8: ...lding fence cover and connection to the antenna is made via a BNC connector The RF IF supplies 5 volts to the antenna s preamplifier through this BNC connector The block diagram in Figure 4 below shows the interaction between components on the RF IF Assembly Figure 4 RF IF Block Diagram 1 2 4 Interface Board and Data Cards The Interface Board provides two way data transfer capability between the M...

Page 9: ...received as a 10 bit data word at the 26 pin rear connector Diode isolation on these input lines pre vents damage to the GPS 155 The data is then decoded and output to the Main Board data bus via the Interface Board The Altitude Decoder Board also provides a discrete input for the GPS SEQ switch When grounded this line activates the GPS 155 s HOLD mode This input is sent to the Main Board data bus...

Page 10: ...n Board see Section 3 2 4 Data card failed Replace NavData card Replace Interface Board see Section 3 2 3 Data card write fail Replace user data card Replace Interface Board see Section 3 2 3 Fuel Air input fail Check connections to fuel air data system Replace Main Board see Section 3 2 4 Memory battery low Replace memory battery see Section 4 1 No altitude input Verify connections to altitude se...

Page 11: ... 8 and 5 2 volts If the voltage is out of the limits specified replace the Main Board 3 Check the DC voltage between D804 and ground as shown in Figure 5 The voltage should be between 48 00 and 72 00 volts If the voltage is out of the limits specified replace the Main Board 4 Check the DC voltage between I806 pin 1 and ground as shown in Figure 6 The voltage should be between 11 75 and 12 25 volts...

Page 12: ...ard see Section 3 2 4 Unit will not power off Replace Main Board see Section 3 2 4 Replace Control Display Unit see Section 3 2 1 Replace Pwr Dimmer Switch see Section 3 2 7 Display has horizontal or vertical lines Replace Display Board see Section 3 2 9 Replace Main Board see Section 3 2 4 Replace Control Display Unit see Section 3 2 1 Display has missing or dark pixels Replace Display Board see ...

Page 13: ...roach select switch not Check connections and verify operation in Test functioning properly Mode see Section 4 3 2 Replace external switch Replace Main Board see Section 3 2 4 OBS select switch course select Check connections and verify operation in Test or hold not functioning properly Mode see Section 4 3 2 Replace external switch Replace Altitude Decoder Board see Section 3 2 2 Replace Main Boa...

Page 14: ...be considered a problem However this should seldom occur in 3D mode 4The Turning Off message appears at below approximately 9 VDC external power SECTION 3 DISASSEMBLY INSTRUCTIONS To avoid damaging the GPS 155 s circuit boards and assemblies the following procedures should be carefully followed Assembly drawings are included in Section 5 for reference Figures 12 through 15 NOTE The NavData card sh...

Page 15: ...102 and the power dimmer switch 3 2 2 Altitude Decoder Board 012 00090 00 Removal 1 Remove the covers as described in Section 3 1 2 Disconnect the battery pack wiring harness from the 3 pin connector J800 on the Main Board see Figures 5 and 12 3 Remove the two 4 40 standoffs 211 63234 08 which hold the 26 pin DSUB connector to the chassis 4 Carefully pull the Altitude Decoder Board toward the fron...

Page 16: ...or J804 Pull up on the retaining lip of the ZIF connector Gently pull the flexible circuit cable out of the ZIF connector Take care not to crease the flexible circuit cable 10 Remove the two 4 40 standoffs 211 63204 08 which hold the 37 pin DSUB connector to the chassis 11 Remove the M3 x 5mm screw 211 50227 05 and the M3 x 10mm screw 211 50227 15 holding the Main Board to the chassis 12 Carefully...

Page 17: ...Remove the three M3 x 5mm screws 211 50227 05 securing the battery pack to the chassis Note One screw is recessed in a hole on the side of the battery pack 6 Slide the battery pack cable and connector P800 through the cutout in the chassis 3 2 7 Power Dimmer Switch 011 CS032 00 Removal 1 Remove the covers as described in Section 3 1 2 Remove the Control Display Unit as described in Section 3 2 1 3...

Page 18: ...pointed away from the chassis frame 2 Ensure that the power dimmer switch is in the off position 3 Slide the battery pack connector P800 and cable into the cutout in the chassis 4 Mount the battery pack to the chassis using three M3 x 5mm screws 211 50227 05 5 Attach the RF IF Assembly to the Main Board by reversing the steps followed in Section 3 2 5 6 Mount the Main Board Sub Assembly on the cha...

Page 19: ... RF IF Assembly to the Main Board 4 Carefully pull the RF IF Assembly upward disengaging it from the Main Board Connector J803 Place the RF IF Assembly to the side of the unit NOTE With the mounting screws removed the cover for the RF IF Assembly will be loose Grip the RF IF Assembly firmly by the sides instead of by its cover when lifting upward 5 Remove the old battery by gently pushing it towar...

Page 20: ... P N T00 00007 00 is contoured for insertion into either of the two extraction cavities on the chip carrier socket Remove the chip by inserting the extraction tool with the correct angle see figure 8 and pivoting the tool on its heel against the socket 4 ROM Extraction Procedure a Orient the socket and tool as shown in figure 9 CAUTION Do not attempt to completely extract chip from chip carrier so...

Page 21: ...ing the power dimmer knob clockwise from the off position Verify that the Self Test Page is displayed shows the software version number and copyright notice Also press the MSG key to verify that the Stored data lost message appears on the Message Page and the ROM failed message does not appear Failure to clear memory after ROM replacement can cause unpredictable operating problems 8 Turn the GPS 1...

Page 22: ...7 Turn the FUNCTION SELECT switch to POWER IN Ensure that the PANEL POWER and UNIT POWER push button switches are OFF not lighted 8 Turn on the power supply push the PANEL POWER switch and verify that it lights up Push the UNIT POWER switch and verify that it lights up 9 Monitor the POWER IN voltage with the DMM and set the power supply for 28 0 VDC 10 Push the UNIT POWER switch to turn unit power...

Page 23: ...ise to select TO Verify that the DMM voltage is 83 20 millivolts Units with Mod Status 1 DMM voltage is 190 40 millivolts 4 CDI Nav Flag Test a Rotate the outer function knob clockwise b Turn the FUNCTION SELECT switch on the test panel to position 1 c If necessary rotate the inner function knob to select IN VIEW Verify that the DMM voltage is 0 10 millivolts d Rotate the inner function knob clock...

Page 24: ...1 0 VDC m Rotate the inner function knob to select HIGH Verify that the DMM voltage is greater than 4 5 VDC n Rotate the outer function knob counterclockwise until DATA flashes o Rotate the inner function knob clockwise to select SYNC p Turn the FUNCTION SELECT switch on the test panel to position 16 q Rotate the outer function knob clockwise until LOW flashes Verify that the DMM voltage is less t...

Page 25: ...f e e g C g C hf g g f hf g g f e e B g h g g hf hf g f B g f g g f B e f he C g he e C g hf hf f C f e e C f g e C f e e f B f f f B f f hf f e B B f g B f e B e g f g g g f hf g f g g g f g g C f g C e B f g e B g f g g hf g g f hf g C C f e C hf e B f e hf C g f C hf g g f hf g C g f g f g g f B e C f g e C f e B f g B f e B g g g f e h he h h hf h h e f C he g C f C C he g C f C e f B f g e B ...

Page 26: ...C e g B e g he e B f B f B he B h B g g h he he he B f e B f e h C h he g f f f f hf h f g h he he hf f f g f e B h he f hf g g h B f e e h he he hf g f f B e C h he f hf g f C h f e e h he he hf g f g e B h f f hf hf g f f h f e e h he f f hf g f B e hf C e g C f he hf g f f h C f C C h he C f he g f C e f e B g B f B g hf g f B g f B B h he B f B f g f B g e f g h h g hf g g g h e he hf h f g g ...

Page 27: ...SELECT switch on the test panel to position 11 l Using the voltage reading on the DMM adjust the external power supply to 28 0 VDC 24 e e e f B e g e hf g f g g f e g g g e f e h g e h g f e hf e C f f g f C f C g f C C f C g f C f C f C e e g B e g f B f g f B f f he B f f B h h B he B he B f B f f f e B e e h C h f C f g f f f f f f C h h f hf f hf f f f f f g e e B h f e e f e he f h h g hf g g...

Page 28: ...C 13 GPS Receiver Noise Test a Depress the ENT key while powering up the unit THis puts the unit into Test Mode b Rotate the outer function knob until the Receiver Test Page is displayed c Terminate the GPS receiver s antenna connection into a 50 ohm load d The bottom line of the display represents the receiver noise level Verify that this number is within the range of 1800 2200 14 Operational Tes...

Page 29: ...ith a clear view of the sky through a coax with a 10 dB 1 dB cable loss 1 5 GHz NOTE Attenuation pads must not be used since the unit supplies the GA 56 with DC power A 10 dB cable is available through GARMIN P N 320 00088 00 c Turn on the GPS 155 Go to the Satellite Status Page see Pilot s Guide for instructions d Allow the unit to lock onto the satellites If the unit has current almanac data it ...

Page 30: ... eV Lf f 5g e N f g g g3 L e f he f hf 5h 7 H e e 3 1f f f3 Xe f e J g7 3 e gO h e 5g 5 e hf Lf eN 1 f 5e7 L h Lh7 f N g H T Y he f hJ h f e N X e e N g 5 e L e 5 g f gN 1 e7 H 3L J 5he hf e 0Y he Hh 3 e e V L e f7 L eV 1e Hf e g e fO2 he e N e O2 Y e hf f e Lf He hN 0 4 X g Kf Lg N V hf N 1 fN h h 7 HfN f3 Xe g 1g f 3 1 e H g g M he J e N1 7 Hhe f X h J 5 h L L He 3 LfN Xe f e N L f he N g 7 He h...

Page 31: ...HhfN 1 e J Y J h7 f 1 V X f Lf 5g N N fJ Yg f 7 g3 e7 H J h N f h Hg g h 7 he L e 3 eV Lf f e3 1 e Hf V e J 5 g hf f g 5 h e gW2 5e L e e3 1 fJ 5 3 HhJ h7 5 e N 1g J 7 5 hfJ 5 hf e 6 2 h h fN eN Xe f h 1 3 L e7 H g f 3 g f e L Y h hf e J 5h g h h Hhe H hf f Le V X e f H eV Le Lf e g f fO2 H h e N 1f O Ye e eN f7 H e h Xg H f L f e N h N h L e e 3 1f f 1g J N 1 e h g hf 1 J e 3 e Hhe J f X h g g h ...

Page 32: ...031 00 Power Dimmer Switch w Flex Ckt Cable 011 CS032 00 Rotary Switch Assy w Wiring Harness 011 CS033 00 Display Board Assy 012 00029 00 Main Board Assy 012 00089 00 Interface Assy 012 00031 01 Altitude Decoder Board 012 00090 00 RG 58 10 dB Cable 1 5 GHz 320 00088 00 Lithium Cell 2032 360 00003 01 Wall Charger AC Adapter 362 00010 00 Wall Charger AC Adapter 362 00014 00 Knob Inner w set screws 4...

Page 33: ...NGS The following assembly drawings are provided for part identification and to aid in assembly disassem bly of the GPS 155 Figure 12 GPS 155 Assembly Drawing View 1 30 211 50227 05 211 50227 05 211 50227 05 211 50227 05 ...

Page 34: ...Figure 13 GPS 155 Assembly Drawing View 2 31 211 63234 08 211 63234 08 012 00091 00 012 00091 00 211 50227 15 211 50227 05 ...

Page 35: ...Figure 14 GPS 155 Assembly Drawing View 3 Figure 15 GPS 155 Connector Diagram 32 012 00091 00 P701 J701 011 00127 00 ...

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