I have an Alphaserver 1000A which began intermittently halting, same
as if the halt switch had been pressed. At the time it had a serial
console. I thought it might have been picking up noise on the serial
line and interpreting it as a break signal so I changed over to a
graphics console. It still halted intermittently. This problem either
went away or the following problem caused me to not notice it any more.
The machine started intermittently powering itself down, requiring it
to be switched off and back on again to reset the power supply before
it could be run again. The machine might stay running for several
hours or it might power down less than a second after switching on, or
anything in between.
Thinking that the two problems might be related, I investigated the
operator control panel on which are mounted the low voltage on/off
switch and the halt switch. I found the two switches to have little
in common and my theory to be unlikely to be correct. The on/off
switch and associated circuitry appear to be working correctly, as
does the interlock which cuts power when the lid is removed.
I tried a power supply unit from another Alphaserver 1000A and found
this did not cure the problem so I replaced the original. Thinking
that the power supply might be sensing an overload, I disconnected
the power feeds to the disks/cd/floppy and removed all the PCI cards.
The problem was still there.
When it was failing regularly, I found a line going to the power
supply which normally sat at 0V and pulsed high just as the power
supply shut down. This line did not pulse the same way when the
power was turned off normally. I suspect it is a signal from the
system board to the power supply requesting it to shut down, or
less likely, a signal from the power supply to the system board
signalling it has a problem and is about to shut down.
I have a service guide which mentions the possibilty of the power
supply shutting down due to a fan failure or high temperature but
it doesn't give any details on how this works or even how to find
out if it is happening.
Does anyone have any detailed information about the power control
system in the Alphaserver 1000A or any helpful suggestions?
Regards,
Peter Coghlan.