Mitsubishi Electric Melsec-Q172DCPU User Manual page 207

6 INSPECTION AND MAINTENANCE
1)
Remove all modules other than the
power supply module from the base
unit.
Does "POWER"
LED turn on?
YES
Install all modules that removed from
the base unit to the base unit.
Check the sum of internal current
consumption of the modules that
comprise the system.
Does the total
current exceed the rated
output current of the power
supply module?
NO
A hardware fault
Check operation in the order starting
with the minimum system.
If the module will not work, explain
the error symptom and get advice
from our sales representative for the
modules with failure.
The base unit that includes the
NO
corresponding power module is faulty.
(Replace it with a normal base unit.)
Does "POWER"
LED turn on?
A hardware fault
Explain the error symptom and get
advice from our sales representative.
Reexamine the system configuration
YES
to make the total current less than the
rated output current of the power
supply module.
NO
Does "POWER"
LED turn on?
6 - 18
YES
NO
YES
END