HP 330 Service Information Manual page 171

Live Unit Procedure
A live unit is one which has a motherboard and properly functioning power supply but the
unit will not function. One of the assemblies installed (other than the power supply) is usually
defective. Live units often are very difficult to troubleshoot, since a problem anywhere on a bus
in the computer or bus expander can shut the system down and prevent the execution of any
instructions, even those from the self-test.
The Live Unit Procedure is a method for finding the defective assembly which is preventing the
processor from executing instructions. It assurnes that the power supply is operating properly,
and the self-test tried to run, but didn't.
If the power supply is not operating properly, refer to the Dead Unit Procedure. If the turn-on
self-test runs enough to either display a failure, stalls in a meaningless state, or passes, refer to
the Functional Unit Procedure.
Live Unit Procedure is explained by first assuming either the computer or bus expander is
defective but which one cannot be determined at this time. Depending on the application,
several accessory cards may be installed in both units. Once the problem in the computer
system has been isolated to the computer/bus expander units, it's sometimes best to start with
a minimum configuration.
Minimum Configuration
A rninimum configuration consists of just enough assemblies to function at a minimum level,
but not necessarily correct. For this computer, a minimum functional level is that required to
light the Self-Test LEDs. Minimum hardware to do this is:
• Power Supply.
• Motherboard.
• Processor Board.
• At least 4 Mbytes of RAM configured at the top of memory.
For the bus expander, the minimum functional configuration is:
• Power Supply.
• Motherboard.
• One functional board or card.
Computer Minimum Configuration
To get a minimum configuration in the cornputer, follow these steps after verifying the power
supply functions correctly.
Troubleshooting
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