Tyan Thunder 2462 rebooting problem

Hello all,

I have an odd problem with my computer. Started spontaneously, not a
cause of any hardware change.
When I reboot the computer (start, shut down, restart) the computer does
not restart. It makes the right noises, but the monitor never shows an
image (in fact the standby light never goes to green) and I never get a
beep and it never boots up to OS. When I push the reset button it still
won't reboot, and when I try and turn it off by pushing in and holding
the start button, it will not shut down, but instead tries to restart.
When I turn the machine off at the mains, or with the switch on the PSU,
and leave it a minute before turning back on, it boots fine. Likewise
from the normal cold boot it works as expected: BIOS image on screen,
goes through boot up process, beeps, boots into OS.
I have checked for loose connections, checked the SCSI cabling and
terminations, but still this goes on, repeatedly.
Does this behaviour ring any bells with anyone? Anyone any idea why this
is happening?

Cheers

Mark

Computer is
Tyan Thunder 2462 Motherboard (just over 3 years old)
Tagan 480W PSU (8 months old)
2 x Athlon MP 2600+
4 x SCSI HDD
Nvidia Quadro 980 VGA
2 x Pioneer 109 DVD-Rs
2.5 GB RAM

 

That rings bells with my Tyan S2460 and Tagan 480 Watt PSU behaving in
exactly the same manner. The issue is associated with the PSU warming up. I
think you'll find that if you remove the PCs covers to get extra airflow
through the PSU that the problem goes away and the machine reboots normally.
I believe the Tagan 480 Watt PSU doesn't have very effective thermal fan
speed control so when its to hot it just fails to supply the required
voltages resulting in a failure to reboot.

I bought one of these PSUs about 18 months ago and it behaved in the above
manner until it went pop and stopped working about 6 months ago. A
replacement was supplied and this has so far exhibited the same reboot
problems with the covers on - I've therefore left the PCs side cover off. My
suggestion would be to try a different model of PSU. Its a pity really
because I've otherwise read excellent reviews for the Tagan 480 Watt unit
and its certainly quiet.

The test to confirm the above is to attempt a reboot as soon as the OS has
fully loaded after a long spell of the machine being turned off. Its likely
that will work fine. Now there are improved choices for Tagan PSUs I'm
thinking of approaching Tagan for a "fix" - in the form of a different model
which doesn't have this problem.

Paul

 

Thanks Paul,

Your explanation makes total sense. I shall get on to Tagan straight
away and see what they have to say.

All the best

Mark

 

I'd be interested to know what they have to say if you care to post your
results here! You may wish to mention to them that you'd heard of this
problem with associated failure of PSUs with time.

Paul