IBM Xseries 236 power issues?

Posted on 2009-03-30
Last Modified: 2013-12-11
Just started today. Server shuts down and when it attempts to start up, it shuts back down after 1 second. I can hear fans start and then stop. They start and then stop.  Over and over again, until after a few moments, it just stops. Lights on Power Supply and motherboard are on by the system is not on.  If I pull the Powersupply out and then put it back in it will start up but only last for a few moments.
Question by:dayvid4444
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LVL 95

Expert Comment

by:John Hurst
ID: 24024490
If the Power Supply is in the server, some power will be going some places in the server, so three suggestions:
1. The obvious one - replace the power supply.
2. Less obvious - CPU fault and it is overheating (quickly) and shutting down.
3. Motherboard failure of some kind.

Is the unit under warranty? Whatever, it needs service. IBM are good at servicing their servers.
... Thinkpads_User

Author Comment

ID: 24024518
Wouldn't the CPU fault leave an error in the Event Viewer?  I'm not getting any error messages other than the shutdown was unexpected.
LVL 95

Expert Comment

by:John Hurst
ID: 24024549
I don't know about servers (because I have not had a hardware fault shutdown). But in an IBM computer, a true CPU overheat (in danger of damaging the CPU) shuts down the computer and I don't see any error logs about it. And of course, it may not be the CPU at all in your case.
... Thinkpads_User
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Author Comment

ID: 24024596
will IBM diag on bootup detect if it is CPU?
LVL 95

Expert Comment

by:John Hurst
ID: 24024663
I don't think so, but I don't know for sure. I would certainly try, because such a step might eliminate the CPU as a problem. ... Thinkpads_User
LVL 26

Accepted Solution

PCBONEZ earned 500 total points
ID: 24049013
Power up sequence goes something like this.
Push power button, PSU begins to start up. [Fans and drive motors will start to spin-up now.]
During this time a part of the motherboards chipset [powered by Standby Voltage which is usually +5vsb] is continually resetting the CPU to prevent it from starting. This continues until the PSU has issued the Power Good signal. The reason is by design the CPU is not to be powered before the power supply is stable and there is enough charge in CPU Voltage Regulator Caps to handle the sudden heavy load of the CPU during start-up. If this were not done the CPU Regulators may burn out due to high inrush current. The power supply has ~50 milliseconds to get the caps charged to (something like) 80% of the required voltage.
- - - If PSU isn't up to volts in the 50 milliseconds then the PSU shuts back down to protect the CPU. The assumption is there is a fault in the power distribution and this feature is to protect the CPU. If PSU shuts down the resetting stops because there is no power to the CPU anyway and so nothing to reset.
- - - If PSU is up to volts in less than 50 milliseconds it sends the Power Good signal and that stops the Chipset from sending CPU reset.
Once CPU has power and isn't being reset the POST Code in the BIOS runs and soon you start seeing things on the screen.
May seem like a minute but fans take a LOT longer to spin down than up.
Things that will prevent Power Good from being issued: Shorted Fan, shorted Drive Motor (floppy, optical, zip, or hard drive), shorted USB port or device, shorted PS/2, bad motherboard caps, bad PSU (usually caps), shorts on add-in cards.

Another possibility is a bad CMOS battery believe it or not.
I've had server boards that double-boot after a CMOS setting change to reset stored data.
[I don't fully understand why it's done this way but it is.]
If yours does that and the CMOS battery is dead then the new data isn't saved [CMOS clears instead of storing] and then each and every boot is #1 of the two boots. Instead of going #1-store #2-RUN, it's going #1-store-clear #1-store-clear #1-store-clear #1-store-clear ......


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