IBM 86655RY Hardware Maintenance Manual - Page 41

Table 1. Light path diagnostics. LED PS4 Cause The fourth power supply has failed. Replace the fourth power supply. Action Power checkout Power problems can be difficult to troubleshoot. For instance, a short circuit can exist anywhere on any of the power distribution busses. Usually a short circuit will cause the power subsystem to shut down because of an overcurrent condition. A general procedure for troubleshooting power problems is as follows: 1. Power off the system and disconnect the AC cord(s). 2. Check for loose cables in the power subsystem. Also check for short circuits, for instance if there is a loose screw causing a short circuit on a circuit board. 3. Remove adapters and disconnect the cables and power connectors to all internal and external devices until system is at minimum configuration required for power on (see "Minimum operating requirements" on page 225). 4. Reconnect the AC cord and power on the system. If the system powers up successfully, replace adapters and devices one at a time until the problem is isolated. If system does not power up from minimal configuration, replace FRUs of minimal configuration one at a time until the problem is isolated. To use this method it is important to know the minimum configuration required for a system to power up (see page 225). For specific problems, see "Power error messages" on page 237. Temperature checkout Proper cooling of the system is important for proper operation and system reliability. For a typical Netfinity server, you should make sure: • Each of the drive bays has either a drive or a filler panel installed • Each of the power supply bays has either a power supply or a filler panel installed • The top cover is in place during normal operation • There is at least 50 mm (2 inches) of ventilated space at the sides of the server and 100 mm (4 inches) at the rear of the server • The top cover is removed for no longer than 30 minutes while the server is operating • The processor housing cover covering the processor and memory area is removed for no longer that ten minutes while the server is operating • A removed hot-swap drive is replaced within two minutes of removal • Cables for optional adapters are routed according to the instructions provided with the adapters (ensure that cables are not restricting air flow) • The fans are operating correctly and the air flow is good • A failed fan is replaced within 48 hours In addition, ensure that the environmental specifications for the system are met. See "Features and specifications" on page 3. For more information on specific temperature error messages, see "Temperature error messages" on page 236. Diagnostics 31