Service manual

June 21, 2004 1-29
NP88 FLEX GENERAL
Troubleshooting
FLEX Pagers
1. With the pager in the OFF mode, press the button eight (8) times within 3
secondsto entertheTuningTest modeanddisablethe batterysaver. TheLCD
displays:
2. To exit the test mode, press the button. The status screen is displayed and
the pager is on.
Corrective Maintenance
Corrective maintenance involves two basic procedures: localization/isolation of
trouble, and replacing the defective component.
Fault Isolation
Localization of trouble to a defective circuit in the pager unit is most easily
accomplished by performing the test procedures outlined in the subsequent para-
graphs.Localization involves tracingthetrouble tothedefectivecircuit causingthe
abnormal operation. Isolation means tracing the trouble to a defective component
within the loca lized circuit.
Defining the p roblem is the most important step in the isolat ion of a malfunction.
Inaccuracy of problem definition and unfamil iarity with pager operation can lead
to the introduction of additional problems. With the basic understanding of the
pager operation, problems are isolated by analyzing the following:
• Are most, some, or all pager functions inoperative?
• Which particular modes are inoperative?
Concentrateon troubleshootingcircuitsthatarecommon totheinoperativemodes.
Component Replacement
Integrated circuit s (ICs) are very reliable components and are not replaced unless
it is definitely indicated they are defective.
Before replacing an IC, make sure the external components in the circuit are
normal. Signal tracing with an oscilloscope is the preferred IC testing method. It
provides a visual indication of an input signal condition, its pulses (shape and/or
-----------1
Figure 1-28.
G
Remove circuit components with care. Avoid bending pins. Use anti-static handling
procedures to prevent electrostatic discharge and component damage.
G
Some ICs are not field-replaceable. Attempting to remove and/or replace these
devices can result in damage to the device, the circuit board, or other devices. Refer
to the applicable decoder or receiver servicing supplement for further information.
Self-Diagnostic Feature