Chapter 2 Basic Troubleshooting; Level O (Power-On) Diagnostics - NCR PC4i Service Manual

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Chapter 2
Basic
Troubleshooting
This chapter is intended to help the engineer in
either repairing the system, or bringing it to a
partially operative state so that the diagnostic
diskette may be used for further troubleshooting.
Presented here is a structured sequence of operations
to follow when either the system is unable to run
diagnostics, or the level O (power-on) diagnostics
fail (see
Fig.
2-1).
Generally faulty systems can be classified into two
types:
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Non-operative - a system where it is not possible
to load a diagnostic diskette.
o Partially operative - a system with sufficient
working components to allow the loading of a
diagnostic diskette.
LEVEL O (POWER-OH) DIAGNOSTICS
The level O diagnostics are performed automatically
each time the system is switched on.
These diagnostics check the following:
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RAM memory (for memory size setting refer to
Chapter 8 "Strapping Information")
o 8088 CPU (CPU is used to test all the modules)
o 27182 EPROM (containing BIOS)
o 765 Flex Disk Controller
2-1