Service and troubleshooting 
EST3 Installation and Service Manual  8.3 
Overview 
Maintenance philosophy 
The EST3 life safety system consists of modular assemblies 
utilizing surface mount technology (SMT) for easy installation 
and maintenance. SMT provides high reliability but prohibits 
component-level field repairs. For these and other reasons, the 
maintenance philosophy consists of fault isolating to the circuit 
card assembly, removing the defective circuit card, and then 
replacing it with a spare. 
Service and repair of EST3 system components centers around 
the following assumptions: 
1.  Qualified technicians possessing a complete understanding 
of the system hardware and functions will perform 
maintenance. 
2.  Only certified maintenance technicians will service the 
equipment. 
3. Maintenance technicians will have a ready available supply 
of replacement parts. 
Problem classification 
Problems with the system can generally be classified into two 
categories: application programming problems and hardware 
(including firmware) problems. Many times hardware problems 
are identified by the system itself. Application programming 
problems are typically suspected when an incorrect response 
happens, or when a response fails to happen or happens at the 
wrong time. 
Handling static-sensitive circuit modules 
Many of the circuit modules use components that are sensitive to 
static electricity. To reduce the possibility of damaging these 
components, take the following precautions when handling: 
1.  Use only approved grounding straps that are equipped with a 
1 MΩ resistive path to earth ground. 
2.  Always keep circuit modules in their protective antistatic 
packaging. Remove only for inspection or installation. 
3.  Always hold circuit modules by the sides. Avoid touching 
component leads and connector pins.