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SECTION 1
INTRODUCTION
This manual is intended to provide instructions and guidelines for the maintenance and repair of the
GARMIN GPS 155.
WARNING: This unit contains static sensitive devices. Service personnel must insure that proper precau-
tions are taken to prevent damage to this equipment from Electro-Static Discharge (ESD). Disassembly and
repair should only be accomplished in an approved ESD workstation by properly trained and grounded
personnel.
1.1 GENERAL DESCRIPTION
The GPS 155 is a full-featured aviation GPS navigation instrument that offers not only a fixed panel
mounted installation in its rack, but also provides a take-home capability. The GPS 155 utilizes the patent-
ed GARMIN Multitrac
TM
system for tracking up to eight satellites simultaneously. The unit features a GPS
receiver; a front loading NavData card; and a sealed rechargable battery pack. The unit is constructed from
high quality materials and uses the latest techniques in manufacturing technology.
In order to achieve the desired reliability, 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 are available for field replacement:
Display Board Assembly:
Contains the vacuum fluorescent display and display circuit board.
Rotary Switch Assembly:
Contains dual concentric switch and its assembled wiring harness.
Control/Display Unit:
Contains bezel, buttons, lens, keypad board, light pipes, front insert, plus the Display Board
Assembly and Rotary Switch Assembly.
Main Board:
Printed circuit board which contains the microprocessor, LSI, power supply circuitry, and battery charging components.
Altitude Decoder Board:
Printed circuit board which contains the altitude data decoder circuits and interface circuitry.
Interface Board:
Printed circuit board which connects the main board to the NavData® card and the Altitude Decoder
Board.
RF/IF Assembly:
Module which contains the GPS receiver and high precision crystal oscillator.
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